CVE-2026-99041 is a vulnerability in Linux Kernel
Published on October 23, 2026
ip6_gre: remove obsolete ERSPAN PMTU update
In the Linux kernel, the following vulnerability has been resolved:
ip6_gre: remove obsolete ERSPAN PMTU update
A tc tunnel_key action can attach a METADATA_IP_TUNNEL dst to an skb,
and mirred can redirect it to a native ip6erspan device. The legacy PMTU
update in ip6erspan_tunnel_xmit() treats that metadata dst as a route.
Since it has no output device, dst_dev(dst)->mtu dereferences NULL.
On v7.2 with KASAN, an initial UID/GID 65534 process with CapEff 0 used
self-created user and network namespaces to trigger:
KASAN: null-ptr-deref
RIP: ip6erspan_tunnel_xmit+0x10fc/0x2cc0
Kernel panic - not syncing: Fatal exception in interrupt
The update is obsolete. Commit fe1a4ca0a2b7 ("ip6_gre: process toobig
in a better way") changed IPv6 GRE Too Big handling to update the
underlay route and removed the equivalent block from __gre6_xmit().
ip6_tnl_xmit() then propagates the underlay PMTU to the overlay route.
Remove the stale ERSPAN copy and its now-unused dst variable. This
eliminates the metadata-dst dereference and keeps ERSPAN aligned with
IPv6 GRE PMTU handling.
Products Associated with CVE-2026-99041
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Affected Versions
Linux:- Version 5a963eb61b7c39e6c422b6e48619d19d04719358 and below b14a682ad7d45345701e08f9279d483a1da8b36c is affected.
- Version 5a963eb61b7c39e6c422b6e48619d19d04719358 and below f5b143f4cd3fb7673df8d727550478a4b762908a is affected.
- Version 5a963eb61b7c39e6c422b6e48619d19d04719358 and below 2d06cb25a497d3a7034ef9d172626c2d6620a0f1 is affected.
- Version 5a963eb61b7c39e6c422b6e48619d19d04719358 and below 8f27260b989f488760289276377db24fbfb20bfa is affected.
- Version 5a963eb61b7c39e6c422b6e48619d19d04719358 and below 8bc60db48e8cba35488bbd6e1f94aa990afa275a is affected.
- Version 4.16 is affected.
- Before 4.16 is unaffected.
- Version 6.6.160, <= 6.6.* is unaffected.
- Version 6.12.114, <= 6.12.* is unaffected.
- Version 6.18.58, <= 6.18.* is unaffected.
- Version 7.2.11, <= 7.2.* is unaffected.
- Version 7.3, <= * is unaffected.