CVE-2026-68431 is a vulnerability in Linux Kernel
Published on August 12, 2026
ksmbd: validate minimum PDU size for transform requests
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: validate minimum PDU size for transform requests
The receive path applies the minimum SMB2 PDU size check only when
ProtocolId is SMB2_PROTO_NUMBER. A packet carrying
SMB2_TRANSFORM_PROTO_NUM bypasses the check even when the negotiated
dialect does not provide transform handling.
On an SMB 2.1 connection, a short transform packet therefore reaches
init_smb2_rsp_hdr(), which interprets the request as a full SMB2 header
and reads beyond the request allocation. The copied fields can then be
returned to the unauthenticated client.
Compression transforms are converted to ordinary SMB2 messages before
protocol validation. After that conversion, validate ordinary SMB2
requests against SMB2_MIN_SUPPORTED_PDU_SIZE and require encryption
transform requests to contain both a transform header and an SMB2
header. This rejects truncated requests before work allocation.
Products Associated with CVE-2026-68431
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Affected Versions
Linux:- Version 368ba06881c395f1c9a7ba22203cf8d78b4addc0 and below b62c510f59803f82f9b4c76ead2a56833b2984c7 is affected.
- Version 368ba06881c395f1c9a7ba22203cf8d78b4addc0 and below cfc0b8e5080aec87700774e8568765eaa4b7b92b is affected.
- Version df3a4518aee64f21bcafa891105b468413f27431 is affected.
- Version 543c12c2644e772caa6880662c2a852cfdc5a10c is affected.
- Version e9cb7be2fcbaee9e808b729e92948d38d52e5add is affected.
- Version 5.15.145 and below 5.16 is affected.
- Version 6.1.34 and below 6.2 is affected.
- Version 6.3.8 and below 6.4 is affected.
- Version 6.4 is affected.
- Before 6.4 is unaffected.
- Version 7.1.6, <= 7.1.* is unaffected.
- Version 7.2-rc5, <= * is unaffected.