Canonical Ubuntu Linux Linux Operating System

GnuTLS PKCS#7 Padding Timing SideChannel Info Disclosure
CVE-2026-5419 3.7 - Low - June 01, 2026

A flaw was found in gnutls. The PKCS#7 padding check, performed during decryption, was not constant-time. This timing side-channel could allow a remote attacker to potentially leak sensitive information about the padding bytes through observable timing differences. This vulnerability is a form of information disclosure.

Observable Timing Discrepancy

Null Deref in AF_INET/AF_INET6 Oops on Ubuntu Kernel 6.8/6.17/7.0
CVE-2026-47337 3.3 - Low - May 28, 2026

Ubuntu Linux 6.8, 6.17 and 7.0 contain SAUCE patches with a possible NULL pointer dereference in the handling of AF_INET/AF_INET6 socket mediation. The bug can be triggered by an unprivileged local user. This can lead to a kernel oops.

NULL Pointer Dereference

Ubuntu 6.8 AppArmor Socket Mediation Uninitialized Variable
CVE-2026-47336 3.3 - Low - May 28, 2026

Ubuntu Linux 6.8 contains SAUCE patches with a possible use of an uninitialized variable in AppArmor AF_INET/AF_INET6 socket mediation code. The bug can be triggered by an unprivileged local user and could result in incorrect fine-grained mediation of network sockets.

Use of Uninitialized Variable

Ubuntu 6.8: Null Deref in AppArmor SAUCE, Local Kernel Panic
CVE-2026-47335 5.5 - Medium - May 28, 2026

Ubuntu Linux 6.8 contains SAUCE patches with a possible NULL pointer dereference in the handling of AppArmor notifications. The bug can be triggered by an unprivileged local user. This can lead to a kernel panic.

NULL Pointer Dereference

AppArmor SAUCE bug in Ubuntu kernel 6.8/6.17/7.0 causes panic/deadlock
CVE-2026-47334 5.5 - Medium - May 28, 2026

Ubuntu Linux 6.8, 6.17 and 7.0 contain AppArmor SAUCE patches which incorrectly sleep while holding a spinlock in notification handling code. The bug can be triggered by an unprivileged local user and can result in kernel panic or deadlock.

Deadlock

Ubuntu Linux 6.8/6.17/7.0 AppArmor SAUCE OOB Heap Read via buffer size miscalc
CVE-2026-47333 7.8 - High - May 28, 2026

Ubuntu Linux 6.8, 6.17 and 7.0 contain AppArmor SAUCE patches which can potentially incorrectly compute the size of an internal buffer, leading to a heap memory out-of-bounds read in notification handling code. The bug can be triggered by an unprivileged local user and can result in invalid data being processed by the AppArmor DFA policy engine.

Out-of-bounds Read

Ubuntu Linux 6.8,6.17,7.0 AppArmor SAUCE OOB Read Vulnerability
CVE-2026-47332 5.5 - Medium - May 28, 2026

Ubuntu Linux 6.8, 6.17 and 7.0 contain AppArmor SAUCE patches which incorrectly validate the size of an internal structure, leading to an out-of-bounds read in notification handling code. The bug can be triggered by an unprivileged local user and can result in information disclosure from adjacent slab objects.

Out-of-bounds Read

AppArmor SAUCE UAF in Ubuntu 6.8 kernel due to missing lock
CVE-2026-47331 7.8 - High - May 28, 2026

Ubuntu Linux 6.8 contains AppArmor SAUCE patches which fail to acquire a lock when modifying a linked list. An unprivileged local user could trigger the race condition that can lead to a use-after-free (UAF) and, theoretically, arbitrary code execution.

Dangling pointer

Ubuntu AppArmor SAUCE Uninit Var Bug (6.8/7.x) Wrong Caching
CVE-2026-47330 3.3 - Low - May 28, 2026

Ubuntu Linux 6.8, 7.17 and 7.0 contain AppArmor SAUCE patches which can, under certain circumstances, use an uninitialized variable in notification handling code. The bug can be triggered by an unprivileged local user and can result in the incorrect caching of AppArmor notification responses.

Use of Uninitialized Variable

Local User Crafted AppAmor Name Field in Ubuntu 6.8/6.17/7.0 SAUCE
CVE-2026-47329 3.3 - Low - May 28, 2026

Ubuntu Linux 6.8, 6.17 and 7.0 contain SAUCE patches which fail to validate invalid sizes of the name field in AppAmor notification responses. The bug can be triggered by an unprivileged local user and could result in handling of crafted responses.

Improper Validation of Specified Quantity in Input

Ubuntu 6.8/6.17/7.0 AppArmor SAUCE Pointer Free CVE-2026-47328
CVE-2026-47328 6.1 - Medium - May 28, 2026

Ubuntu Linux 6.8, 6.17 and 7.0 contain AppArmor SAUCE patches which incorrectly attempt to free a pointer which was not previously kmalloc()d, while at the same time leaking allocated memory. The bug can be triggered by an unprivileged local user and can result in the corruption of slab metadata and could lead to resource exhaustion.

Free of Memory not on the Heap

Ubuntu Kernel 6.87.0 NULL Deref in AppArmor (Local) fixed 7.1
CVE-2026-47327 3.3 - Low - May 28, 2026

Ubuntu Linux 6.8, 6.17 and 7.0 contain SAUCE patches with a possible NULL pointer dereference in the handling of AppArmor notifications. The bug can be triggered by an unprivileged local user. This can lead to a kernel oops.

NULL Pointer Dereference

AppArmor SAUCE memory leak causing resource exhaustion in Ubuntu 6.8/6.17/7.0
CVE-2026-47326 5.5 - Medium - May 28, 2026

Ubuntu Linux 6.8, 6.17 and 7.0 contain SAUCE patches with a memory leak in the handling of big responses to AppArmor notifications. The bug can be triggered by an unprivileged local user. The memory leak could lead to resource exhaustion.

Memory Leak

Samba Remote Cmd Exec via Unsanitized %u in check password script
CVE-2026-4408 9 - Critical - May 28, 2026

A flaw was found in Samba. A remote attacker can exploit a misconfiguration in Samba file servers and classic domain controllers that use the "check password script" feature. If this script is configured with the %u substitution character, the client-controlled username is passed without proper escaping of shell meta-characters. This vulnerability allows an attacker to achieve remote command execution on the affected system. This issue primarily affects non-standard configurations where the "check password script" is used with %u and the samba-dcerpcd service is started as a system service.

Shell injection

Linux Kernel AEAD AIO IV Snapshot Vulnerability
CVE-2026-46028 - May 27, 2026

In the Linux kernel, the following vulnerability has been resolved: crypto: algif_aead - snapshot IV for async AEAD requests AF_ALG AEAD AIO requests currently use the socket-wide IV buffer during request processing. For async requests, later socket activity can update that shared state before the original request has fully completed, which can lead to inconsistent IV handling. Snapshot the IV into per-request storage when preparing the AEAD request, so in-flight operations no longer depend on mutable socket state.

Linux Kernel RxRPC Decrypt Packet Leakage Vulnerability (CVE-2026-46000)
CVE-2026-46000 - May 27, 2026

In the Linux kernel, the following vulnerability has been resolved: rxrpc: Fix conn-level packet handling to unshare RESPONSE packets The security operations that verify the RESPONSE packets decrypt bits of it in place - however, the sk_buff may be shared with a packet sniffer, which would lead to the sniffer seeing an apparently corrupt packet (actually decrypted). Fix this by handing a copy of the packet off to the specific security handler if the packet was cloned.

Linux Kernel rxrpc: UAF Fix after skb_unshare() failure
CVE-2026-45998 - May 27, 2026

In the Linux kernel, the following vulnerability has been resolved: rxrpc: Fix potential UAF after skb_unshare() failure If skb_unshare() fails to unshare a packet due to allocation failure in rxrpc_input_packet(), the skb pointer in the parent (rxrpc_io_thread()) will be NULL'd out. This will likely cause the call to trace_rxrpc_rx_done() to oops. Fix this by moving the unsharing down to where rxrpc_input_call_event() calls rxrpc_input_call_packet(). There are a number of places prior to that where we ignore DATA packets for a variety of reasons (such as the call already being complete) for which an unshare is then avoided. And with that, rxrpc_input_packet() doesn't need to take a pointer to the pointer to the packet, so change that to just a pointer.

Samba NTFS Reparse Points Access Control Bypass via SMB
CVE-2026-1933 7.1 - High - May 27, 2026

A flaw was found in Sambas handling of NTFS-style reparse points on shares configured with read only = yes. Due to missing SMB-layer access checks, authenticated users with underlying filesystem write permissions may create or delete reparse point metadata through SMB operations even on read-only exports. This could allow modification of SMB-visible file behavior, including converting files into symbolic links or other reparse point types.

Authorization

AppArmor NULL ptr deref in __unix_needs_revalidation (Linux kernel)
CVE-2026-45966 - May 27, 2026

In the Linux kernel, the following vulnerability has been resolved: apparmor: fix NULL pointer dereference in __unix_needs_revalidation When receiving file descriptors via SCM_RIGHTS, both the socket pointer and the socket's sk pointer can be NULL during socket setup or teardown, causing NULL pointer dereferences in __unix_needs_revalidation(). This is a regression in AppArmor 5.0.0 (kernel 6.17+) where the new __unix_needs_revalidation() function was added without proper NULL checks. The crash manifests as: BUG: kernel NULL pointer dereference, address: 0x0000000000000018 RIP: aa_file_perm+0xb7/0x3b0 (or +0xbe/0x3b0, +0xc0/0x3e0) Call Trace: apparmor_file_receive+0x42/0x80 security_file_receive+0x2e/0x50 receive_fd+0x1d/0xf0 scm_detach_fds+0xad/0x1c0 The function dereferences sock->sk->sk_family without checking if either sock or sock->sk is NULL first. Add NULL checks for both sock and sock->sk before accessing sk_family.

Sambas vfs_worm Rename Bypass Enables Overwrite of WORM Files
CVE-2026-2340 6.5 - Medium - May 27, 2026

A flaw was found in Sambas vfs_worm module. The module is intended to provide write-once, read-many (WORM) protections by preventing modification of files after a configurable grace period. Due to insufficient validation during rename operations, an authenticated user with write access to a share could overwrite a protected file by renaming a newly created file over the existing WORM-protected file.

Improper Handling of Insufficient Permissions or Privileges

Samba CA AutoEnroll HTTP Trust Misinstall (CVE-2026-3012)
CVE-2026-3012 8 - High - May 27, 2026

A flaw was found in Sambas certificate auto-enrollment Group Policy handling. When certificate auto-enrollment is enabled, Samba may retrieve a CA certificate over an unencrypted HTTP connection and install it into the local trust store without proper verification. An attacker with the ability to intercept or redirect network traffic could exploit this behavior to supply a malicious certificate authority certificate, potentially allowing interception or spoofing of trusted communications.

Insufficient Verification of Data Authenticity

GnuTLS SAN Size ForkCheck Bypass
CVE-2026-42013 8.2 - High - May 26, 2026

A flaw was found in gnutls. When validating certificates, an oversized Subject Alternative Name (SAN) could cause the validation process to incorrectly fall back to checking the Common Name (CN) field. This could allow a remote attacker to bypass proper certificate validation, potentially leading to spoofing or man-in-the-middle attacks.

Improper Validation of Specified Quantity in Input

GnuTLS PKCS#12 Bag Off-by-One Buffer Overwrite
CVE-2026-42015 5.3 - Medium - May 26, 2026

A flaw was found in gnutls. An off-by-one error exists in the PKCS#12 bag element bounds check. This vulnerability allows an remote attacker to write past the internal array of a PKCS#12 bag when appending to a bag that already contains 32 elements. This memory corruption could lead to a denial of service (DoS) or potentially other unspecified impacts.

off-by-five

GNUTLS Certificate Validation Bypass via URI/SRV SAN Fallback
CVE-2026-42012 7.1 - High - May 26, 2026

A flaw was found in gnutls. A remote attacker could exploit this vulnerability by presenting a specially crafted certificate that contains Uniform Resource Identifier (URI) or Service (SRV) Subject Alternative Names (SANs). This could cause the certificate validation process to incorrectly fall back to checking DNS hostnames against the Common Name (CN), potentially allowing the attacker to spoof legitimate services or intercept sensitive information.

Improper Certificate Validation

Libgnutls RSA PKCS#11 Key Exchange Overread Info Disclosure
CVE-2026-5260 8.2 - High - May 26, 2026

A flaw was found in libgnutls. A remote attacker, by sending an extremely short premaster secret during an RSA key exchange to a server using an RSA key backed by a PKCS#11 token, could trigger a short heap overread. This memory corruption vulnerability could lead to information disclosure.

Improper Validation of Specified Quantity in Input

Shell Injection in Samba Print Service via Unescaped %J
CVE-2026-4480 9 - Critical - May 26, 2026

A flaw was found in the Samba printing subsystem. Samba passes the client-controlled job description string to the command configured with the "print command" setting via the "%J" substitution character without escaping shell meta characters. A remote attacker could exploit this vulnerability by sending a specially crafted print job description that contains unescaped shell characters. This could lead to remote code execution on the affected system.

Shell injection

Linux kernel: skb sharedfrag flag mispropagated in fragtransfer helpers
CVE-2026-46300 7.8 - High - May 23, 2026

In the Linux kernel, the following vulnerability has been resolved: net: skbuff: preserve shared-frag marker during coalescing skb_try_coalesce() can attach paged frags from @from to @to. If @from has SKBFL_SHARED_FRAG set, the resulting @to skb can contain the same externally-owned or page-cache-backed frags, but the shared-frag marker is currently lost. That breaks the invariant relied on by later in-place writers. In particular, ESP input checks skb_has_shared_frag() before deciding whether an uncloned nonlinear skb can skip skb_cow_data(). If TCP receive coalescing has moved shared frags into an unmarked skb, ESP can see skb_has_shared_frag() as false and decrypt in place over page-cache backed frags. Propagate SKBFL_SHARED_FRAG when skb_try_coalesce() transfers paged frags. The tailroom copy path does not need the marker because it copies bytes into @to's linear data rather than transferring frag descriptors.

Linux Kernel: Preserve SKBFL_SHARED_FRAG marker during skb coalescing
CVE-2026-43503 8.8 - High - May 23, 2026

In the Linux kernel, the following vulnerability has been resolved: net: skbuff: propagate shared-frag marker through frag-transfer helpers Two frag-transfer helpers (__pskb_copy_fclone() and skb_shift()) fail to propagate the SKBFL_SHARED_FRAG bit in skb_shinfo()->flags when moving frags from source to destination. __pskb_copy_fclone() defers the rest of the shinfo metadata to skb_copy_header() after copying frag descriptors, but that helper only carries over gso_{size,segs, type} and never touches skb_shinfo()->flags; skb_shift() moves frag descriptors directly and leaves flags untouched. As a result, the destination skb keeps a reference to the same externally-owned or page-cache-backed pages while reporting skb_has_shared_frag() as false. The mismatch is harmful in any in-place writer that uses skb_has_shared_frag() to decide whether shared pages must be detoured through skb_cow_data(). ESP input is one such writer (esp4.c, esp6.c), and a single nft 'dup to <local>' rule -- or any other nf_dup_ipv4() / xt_TEE caller -- is enough to land a pskb_copy()'d skb in esp_input() with the marker stripped, letting an unprivileged user write into the page cache of a root-owned read-only file via authencesn-ESN stray writes. Set SKBFL_SHARED_FRAG on the destination whenever frag descriptors were actually moved from the source. skb_copy() and skb_copy_expand() share skb_copy_header() too but linearize all paged data into freshly allocated head storage and emerge with nr_frags == 0, so skb_has_shared_frag() returns false on its own; they need no change. The same omission exists in skb_gro_receive() and skb_gro_receive_list(). The former moves the incoming skb's frag descriptors into the accumulator's last sub-skb via two paths (a direct frag-move loop and the head_frag + memcpy path); the latter chains the incoming skb whole onto p's frag_list. Downstream skb_segment() reads only skb_shinfo(p)->flags, and skb_segment_list() reuses each sub-skb's shinfo as the nskb -- both p and lp must carry the marker. The same omission also exists in tcp_clone_payload(), which builds an MTU probe skb by moving frag descriptors from skbs on sk_write_queue into a freshly allocated nskb. The helper falls into the same family and warrants the same fix for consistency; no TCP TX-side in-place writer is currently known to reach a user page through this gap, but a future consumer depending on the marker would regress silently. The same omission exists in skb_segment(): the per-iteration flag merge takes only head_skb's flag, and the inner switch that rebinds frag_skb to list_skb on head_skb-frags exhaustion does not fold the new frag_skb's flag into nskb. Fold frag_skb's flag at both sites so segments drawing frags from frag_list members carry the marker.

Heap Overflow in ngx_http_rewrite_module (NGINX) via PCRE Capture Overlap
CVE-2026-9256 8.1 - High - May 22, 2026

NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_rewrite_module module. This vulnerability exists when a rewrite directive uses a regex pattern with distinct, overlapping Perl-Compatible Regular Expression (PCRE) captures (for example, ^/((.*))$) and a replacement string that references multiple such captures (for example, $1$2) in a redirect or arguments context. An unauthenticated attacker along with conditions beyond their control can exploit this vulnerability by sending crafted HTTP requests. This may cause a heap buffer overflow in the NGINX worker process leading to a restart. Additionally, attackers can execute code on systems with Address Space Layout Randomization (ASLR) disabled or when the attacker can bypass ASLR. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Heap-based Buffer Overflow

Linux Kernel: RDS op_nents double free on zerocopy fail
CVE-2026-43494 7.8 - High - May 21, 2026

In the Linux kernel, the following vulnerability has been resolved: net/rds: reset op_nents when zerocopy page pin fails When iov_iter_get_pages2() fails in rds_message_zcopy_from_user(), the pinned pages are released with put_page(), and rm->data.op_mmp_znotifier is cleared. But we fail to properly clear rm->data.op_nents. Later when rds_message_purge() is called from rds_sendmsg() the cleanup loop iterates over the incorrectly non zero number of op_nents and frees them again. Fix this by properly resetting op_nents when it should be in rds_message_zcopy_from_user().

BIND 9 Unbounded Resend Loop Causing Resource Exhaustion (9.18.369.18.48)
CVE-2026-5950 5.3 - Medium - May 20, 2026

An unbounded resend loop vulnerability exists in the BIND 9 resolver state machine during bad-server handling, enabling a remote unauthenticated attacker to cause severe resource exhaustion by sending queries that trigger specific retry conditions. This issue affects BIND 9 versions 9.18.36 through 9.18.48, 9.20.8 through 9.20.22, 9.21.7 through 9.21.21, 9.18.36-S1 through 9.18.48-S1, and 9.20.9-S1 through 9.20.22-S1.

Unchecked Input for Loop Condition

BIND9 9.20.0-9.21.21/use-after-free via SIG(0) race during recursiveclient limit
CVE-2026-5947 7.5 - High - May 20, 2026

Undefined behavior may result due to a race condition leading to a use-after-free violation. If BIND receives an incoming DNS message signed with SIG(0), it begins work to validate that signature. If, during that validation, the "recursive-clients" limit is reached (as would occur during a query flood), and that same DNS message is discarded per the limit, there is a brief window of time while the SIG(0) validation may attempt to read the now-discarded DNS message. This issue affects BIND 9 versions 9.20.0 through 9.20.22, 9.21.0 through 9.21.21, and 9.20.9-S1 through 9.20.22-S1. BIND 9 versions 9.18.28 through 9.18.49 and 9.18.28-S1 through 9.18.49-S1 are NOT affected.

Race Condition

BIND 9 named Assertion Failure on Non-IN DNS Messages 9.119.21 CVE-2026-5946
CVE-2026-5946 7.5 - High - May 20, 2026

Multiple flaws have been identified in `named` related to the handling of DNS messages whose CLASS is not Internet (`IN`) for example, `CHAOS` or `HESIOD`, or DNS messages that specify meta-classes (`ANY` or `NONE`) in the question section. Specially crafted requests reaching the affected code paths recursion, dynamic updates (`UPDATE`), zone change notifications (`NOTIFY`), or processing of `IN`-specific record types in non-`IN` data can cause assertion failures in `named`. This issue affects BIND 9 versions 9.11.0 through 9.16.50, 9.18.0 through 9.18.48, 9.20.0 through 9.20.22, 9.21.0 through 9.21.21, 9.11.3-S1 through 9.16.50-S1, 9.18.11-S1 through 9.18.48-S1, and 9.20.9-S1 through 9.20.22-S1.

Improper Input Validation

Use-After-Free in BIND 9 DoH (9.20.09.20.22 / 9.21.09.21.21)
CVE-2026-3593 7.4 - High - May 20, 2026

A use-after-free vulnerability exists within the DNS-over-HTTPS implementation. This issue affects BIND 9 versions 9.20.0 through 9.20.22, 9.21.0 through 9.21.21, and 9.20.9-S1 through 9.20.22-S1. BIND 9 versions 9.18.0 through 9.18.48 and 9.18.11-S1 through 9.18.48-S1 are NOT affected.

Dangling pointer

Amplified Resource Consumption in BIND 9 Resolvers (9.11-9.21.21)
CVE-2026-3592 5.3 - Medium - May 20, 2026

BIND resolvers are vulnerable to an amplified resource consumption/exhaustion attack. If a victim resolver makes a query to a specially crafted zone, the resolver will consume disproportionate resources. This issue affects BIND 9 versions 9.11.0 through 9.16.50, 9.18.0 through 9.18.48, 9.20.0 through 9.20.22, 9.21.0 through 9.21.21, 9.11.3-S1 through 9.16.50-S1, 9.18.11-S1 through 9.18.48-S1, and 9.20.9-S1 through 9.20.22-S1.

Incorrect Behavior Order: Early Amplification

BIND 9 TKEY GSS-API Excessive Mem (9.16.50/9.18.48/9.20.22/9.21.21)
CVE-2026-3039 7.5 - High - May 20, 2026

BIND servers that are configured to use TKEY-based authentication via GSS-API tokens are vulnerable to excessive memory consumption when receiving and processing maliciously-constructed packets. Typically these servers will be found in Active Directory integrated DNS deployments and/or Kerberos-secured DNS environments. This issue affects BIND 9 versions 9.0.0 through 9.16.50, 9.18.0 through 9.18.48, 9.20.0 through 9.20.22, 9.21.0 through 9.21.21, 9.9.3-S1 through 9.16.50-S1, 9.18.11-S1 through 9.18.48-S1, and 9.20.9-S1 through 9.20.22-S1.

Missing Reference to Active Allocated Resource

Rsync <=3.4.3 TOCTOU Race Allows Arbitrary File Write/Privilege Escalation
CVE-2026-29518 7 - High - May 20, 2026

Rsync versions before 3.4.3 contain a time-of-check to time-of-use (TOCTOU) race condition in daemon file handling that allows attackers to redirect file writes outside intended directories by replacing parent directory components with symbolic links. Attackers with write access to a module path can exploit this race condition to create or overwrite arbitrary files, potentially modifying sensitive system files and achieving privilege escalation when the daemon runs with elevated privileges. This vulnerability can only be triggered if the chroot setting is false.

TOCTTOU

Unbound 1.141.25 UAF via RPZ XFR Reload Lock Inconsistency
CVE-2026-44608 - May 20, 2026

NLnet Labs Unbound 1.14.0 up to and including version 1.25.0 has a locking inconsistency vulnerability that when certain conditions are met (multi-threaded, RPZ XFR reload, RPZ zone with 'rpz-nsip'/'rpz-nsdname' triggers) it could result in heap use-after-free and eventual crash. An adversary can exploit the vulnerability if conditions are first met on a vulnerable Unbound, i.e., multi-threaded, an RPZ zone with 'rpz-nsip'/'rpz-nsdname' triggers and an ongoing XFR for that RPZ zone. Local RPZ files do not trigger the vulnerability. If the timing is right and an XFR happens at the same time another thread needs to read that RPZ zone, the reader may not hold the lock long enough and the thread applying the XFR may free objects that the reader is about to walk causing the use-after-free. Unbound 1.25.1 contains a patch with a fix to the locking code.

Improper Resource Locking

Unbound <=1.25.0 DoS via unbounded name compression on large RRsets
CVE-2026-44390 - May 20, 2026

NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability when handling replies with very large RRsets that Unbound needs to perform name compression for. Malicious upstream responses with very large RRsets with records that don't share a suffix above the root can cause Unbound to spend a considerable time applying name compression to downstream replies. This can lead to degraded performance and eventually denial of service in well orchestrated attacks. An adversary can exploit the vulnerability by querying Unbound for the specially crafted contents of a malicious zone with very large RRsets. Before Unbound replies to the query it will try to apply name compression which was an unbounded operation that could lock the CPU until the whole packet was complete. A compression limit was introduced in 1.21.1 for this but it didn't account for the case where records would not share any suffix above the root. That causes Unbound to go in a different code path because of the compression tree lookup failure and eventually not increment the compression counter for those operations. Unbound 1.25.1 contains a patch with a fix that increments the compression counter regardless of the compression tree lookup. This is a complement fix to CVE-2024-8508.

Inefficient Algorithmic Complexity

Unbound<=1.25.0: DNS Cache Poison via Promiscuous Authority RRSets
CVE-2026-42960 - May 20, 2026

NLnet Labs Unbound up to and including version 1.25.0 is vulnerable to poisoning via promiscuous records for the authority section. Promiscuous RRSets that complement DNS replies in the authority section can be used to trick Unbound to cache such records. If an adversary is able to attach such records in a reply (i.e., spoofed packet, fragmentation attack) he would be able to poison Unbound's cache. A malicious actor can exploit the possible poisonous effect by injecting RRSets other than NS that are also accompanied by address records in a reply, for example MX. This could be achieved by trying to spoof a reply packet or fragmentation attacks. Unbound would then accept the relative address records in the additional section and cache them if the authority RRSet has enough trust at this point, i.e., in-zone data for the delegation point. Unbound 1.25.1 contains a patch with a fix that disregards address records from the additional section if they are not explicitly relevant only to authority NS records, mitigating the possible poison effect. This is a complement fix to CVE-2025-11411.

Acceptance of Extraneous Untrusted Data With Trusted Data

Unbound DNSSEC Validator DoS via Off-by-Counter in ADDITIONAL Section 1.25.0
CVE-2026-42959 - May 20, 2026

NLnet Labs Unbound up to and including version 1.25.0 has a denial of service vulnerability in the DNSSEC validator that can lead to a crash given malicious upstream replies. When Unbound constructs chase-reply messages for validation, the code uses the wrong counter to calculate write offsets for ADDITIONAL section rrsets. DNAME duplication could increase the ANSWER section count and authority filtering could decrease the AUTHORITY section count and create an uninitialized array slot. Combining these two, the validator later dereferences this uninitialized pointer, causing an immediate process crash. An adversary controlling a DNSSEC-signed domain can trigger this bug with a single query by configuring a DNAME chain with unsigned CNAMEs and a response containing unsigned AUTHORITY records alongside signed ADDITIONAL glue records. Unbound 1.25.1 contains a patch with a fix to use the proper counters to calculate the write offsets.

Access of Uninitialized Pointer

Unbound 1.14.01.25.0 Heap Overflow via EDNS Options
CVE-2026-42944 - May 20, 2026

NLnet Labs Unbound 1.14.0 up to and including version 1.25.0 has a vulnerability that results in heap overflow when encoding multiple NSID and/or DNS Cookie EDNS and/or EDNS Padding options in the reply packet. The relevant options ('nsid', 'answer-cookie', 'pad-responses' (default)) need to be enabled for the vulnerability to be exploited. An adversary who can query Unbound can exploit the vulnerability by attaching multiple NSID and/or DNS Cookie EDNS and/or EDNS Padding options to the query. A flaw in the size calculation of the EDNS field truncates the correct value which allows the encoder to overflow the available space when writing. Those two combined lead to a heap overflow write of Unbound controlled data and eventually a crash. Unbound 1.25.1 contains a patch with a fix to de-duplicate the EDNS options and a fix to prevent truncation of the EDNS field size calculation.

Numeric Truncation Error

DNSSEC Validator NSEC3 Hash Degrad DoS in Unbound <=1.25.0
CVE-2026-42923 - May 20, 2026

NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the DNSSEC validator where the code path to consult the negative cache for DS records does not take into account the limit on NSEC3 hash calculations introduced in 1.19.1. This leads to degradation of service during the attack. An adversary that controls a DNSSEC signed zone can exploit this by signing NSEC3 records with acceptably high iterations for child delegations and querying a vulnerable Unbound. Unbound will keep performing the allowed hash calculations on the NSEC3 records and will not limit the work by the mitigation introduced in 1.19.1. As a side effect, a global lock for the negative cache will be held for the duration of the hashing, blocking other threads that need to consult the negative cache. Coordinated attacks could raise the vulnerability to denial of service. Unbound 1.25.1 contains a patch with a fix to bound the vulnerable code path with the existing limit for NSEC3 hash calculations.

Inefficient Algorithmic Complexity

Unbound 1.25.0 jostle logic flaw can degrade resolution performance
CVE-2026-42534 - May 20, 2026

NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the jostle logic that could defeat its purpose and degrade resolution performance. Retransmits of the same query could renew the age of slow running queries and not allow the jostle logic to see them as aged and potential targets for replacement with new queries. An adversary who can query a vulnerable Unbound and who can control a domain name server that replies slowly and/or maliciously to Unbound's queries can exploit the vulnerability and degrade the resolution performance of Unbound. When Unbound's 'num-queries-per-thread' reaches its limit, the jostle logic kicks in. When a new query comes in, half of the available queries that are also slow to resolve are candidates for replacement. The vulnerability then happens because duplicate queries that need resolution would skew the aging result by using the timestamp of the latest duplicate query instead of the original one that started the resolution effort. Cache and local data response performance remains unaffected. Coordinated attacks could raise this to a denial of resolution service. Unbound 1.25.1 contains a patch with a fix to attach an initial, non-updatable start time for incoming queries that allow the jostle logic to work as intended.

Expected Behavior Violation

Unbound <1.25.1 DoS via Excess EDNS Options
CVE-2026-41292 - May 20, 2026

NLnet Labs Unbound up to and including version 1.25.0 is vulnerable to a degradation of service attack related to parsing long lists of incoming EDNS options. An adversary sending queries with too many EDNS options can hold Unbound threads hostage while they are parsing and creating internal data structures for the options. Coordinated attacks can result in degradation and/or denial of service. Unbound 1.25.1 contains a patch with a fix to limit acceptable incoming EDNS options (100).

Inefficient Algorithmic Complexity

Unbound <1.25.1 TTL Cache Abuse via Ghost Domains
CVE-2026-40622 - May 20, 2026

NLnet Labs Unbound 1.16.2 up to and including version 1.25.0 has a vulnerability of the 'ghost domain names' family of attacks that could extend the ghost domain window by up to one cached TTL configured value. Similar to other 'ghost domain names' attacks, an adversary needs to control a (ghost) zone and be able to query a vulnerable Unbound. A single client NS query can cause Unbound to overwrite the cached expired parent-side referral NS rrset with the child-side apex NS rrset and essentially extend the ghost domain window by up to one cached TTL configured value ('cache-max-ttl'). In configurations where 'harden-referral-path: yes' is used (non-default configuration), no client NS query is required since Unbound implicitly performs that query. Unbound 1.25.1 contains a patch with a fix that does not allow extension of TTLs for (parent) NS records regardless of their trust.

Origin Validation Error

Unbound DNSSEC deep-copy bug (CVE-2026-33278), fixed 1.25.1
CVE-2026-33278 - May 20, 2026

NLnet Labs Unbound 1.19.1 up to and including version 1.25.0 has a vulnerability in the DNSSEC validator that enables denial of service and possible remote code execution as a result of deep copying a data structure and erroneously overwriting a destination pointer. An adversary can exploit the vulnerability by controlling a malicious signed zone and querying a vulnerable Unbound. When DS sub-queries need to suspend validation due to NSEC3 computational budget exhaustion (introduced in Unbound 1.19.1), Unbound deep-copies response messages to preserve them across memory region teardown. A struct-assignment bug overwrites the destination's pointer with the source's pointer. After the sub-query region is freed, the resumed validator dereferences this dangling pointer, triggering a crash or potentially enabling arbitrary code execution. Unbound 1.25.1 contains a patch with a fix to preserve the correct pointer when deep copying the data structure.

Dangling pointer

Unbound <1.25.0 DNSCrypt denialofservice (heap overflow)
CVE-2026-32792 - May 20, 2026

NLnet Labs Unbound 1.6.2 up to and including version 1.25.0 has a denial of service vulnerability when compiled with DNSCrypt support ('--enable-dnscrypt'). A bad DNSCrypt query could underflow Unbound's DNSCrypt packet reading procedure that may lead to heap overflow. A malicious actor can exploit the vulnerability with a single bad DNSCrypt query that its decrypted plaintext consists entirely of '0x00' bytes and does not contain the expected '0x80' marker. Unbound would then start reading more bytes than necessary until it finds a non-'0x00' byte. Based on the underlying memory allocator and the memory layout, it could lead to heap overflow while reading followed by a crash. Likelihood of a crash is low, since it relies heavily on the underlying memory allocator and the memory layout. If the heap overflow does not happen, Unbound's later packet checks will deny the packet. Unbound 1.25.1 contains a patch with a fix to bound reading in the given buffer space.

Improper Handling of Missing Special Element

Rsync Hostname-based ACL bypass <3.4.3: Auth bypass via PTR
CVE-2026-43617 4.8 - Medium - May 20, 2026

Rsync version 3.4.2 and prior contain an authorization bypass vulnerability in the rsync daemon's hostname-based access control list enforcement when configured with chroot. Attackers can bypass hostname-based deny rules by controlling the PTR record for their source IP address, allowing connections from hostnames that administrators intended to deny when reverse DNS resolution fails and defaults to UNKNOWN.

Authentication Bypass by Alternate Name

Rsync 3.4.2 and earlier Integer Overflow in compressed-token decoder
CVE-2026-43618 8.1 - High - May 20, 2026

Rsync version 3.4.2 and prior contain an integer overflow vulnerability in the compressed-token decoder where a 32-bit signed counter is not checked for overflow, allowing a malicious sender to trigger an overflow that causes the receiver process to read and return data from outside the intended buffer bounds. Attackers can exploit this vulnerability to disclose process memory contents including environment variables, passwords, heap and stack data, and library memory pointers, significantly reducing ASLR effectiveness and facilitating further exploitation.

Integer Overflow or Wraparound