CVE-2026-46244: netfilter: nft_inner: Fix IPv6 inner_thoff desync

CVE-2026-46244: netfilter: nft_inner: Fix IPv6 inner_thoff desync

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

netfilter: nft_inner: Fix IPv6 inner_thoff desync

In nft_inner_parse_l2l3(), when processing inner IPv6 packets,
ipv6_find_hdr() correctly computes the transport header offset
traversing all extension headers, but the result is immediately
overwritten with nhoff + sizeof(_ip6h) (40 bytes), which only
accounts for the IPv6 base header. This creates a desync between
inner_thoff (wrong — points to extension header start) and l4proto
(correct — e.g., IPPROTO_TCP), enabling transport header forgery
and potential firewall bypass. This issue affects stable versions
from Linux 6.2.

For comparison, the normal (non-inner) IPv6 path correctly
preserves ipv6_find_hdr()'s result. Removing the incorrect overwrite
ensures that ipv6_find_hdr()'s calculated transport header offset is
preserved, thereby fixing the desynchronization.

The Linux kernel CVE team has assigned CVE-2026-46244 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.2 with commit 3a07327d10a09379315c844c63f27941f5081e0a and fixed in 6.6.142 with commit c161ad9157f5a0429b5ff94d9770faf3bf48d273
	Issue introduced in 6.2 with commit 3a07327d10a09379315c844c63f27941f5081e0a and fixed in 6.12.92 with commit 870d59e2cf218e7418491e26bad768cb16654582
	Issue introduced in 6.2 with commit 3a07327d10a09379315c844c63f27941f5081e0a and fixed in 6.18.34 with commit 689bbf48c1f45130086ae1c46ab83ea4c753c601
	Issue introduced in 6.2 with commit 3a07327d10a09379315c844c63f27941f5081e0a and fixed in 7.0.11 with commit d0f98a3617f6ae5b1e95cde1e68e7ead4a1279ce
	Issue introduced in 6.2 with commit 3a07327d10a09379315c844c63f27941f5081e0a and fixed in 7.1-rc5 with commit b6a91f68ebfed9c38e0e9150f58a9b85da07181c

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-46244
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	net/netfilter/nft_inner.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/c161ad9157f5a0429b5ff94d9770faf3bf48d273
	https://git.kernel.org/stable/c/870d59e2cf218e7418491e26bad768cb16654582
	https://git.kernel.org/stable/c/689bbf48c1f45130086ae1c46ab83ea4c753c601
	https://git.kernel.org/stable/c/d0f98a3617f6ae5b1e95cde1e68e7ead4a1279ce
	https://git.kernel.org/stable/c/b6a91f68ebfed9c38e0e9150f58a9b85da07181c