CVE-2026-46244
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.
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A critical vulnerability in the Linux kernel's netfilter subsystem can allow attackers to bypass firewall rules. The flaw exists in how IPv6 inner packets are parsed, leading to a synchronization error that can be exploited to forge transport headers and evade security filters.
Relevant roles
Severity
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:NEPSS
Technical 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.
References
- https://git.kernel.org/stable/c/689bbf48c1f45130086ae1c46ab83ea4c753c601
- https://git.kernel.org/stable/c/870d59e2cf218e7418491e26bad768cb16654582
- https://git.kernel.org/stable/c/b6a91f68ebfed9c38e0e9150f58a9b85da07181c
- https://git.kernel.org/stable/c/c161ad9157f5a0429b5ff94d9770faf3bf48d273
- https://git.kernel.org/stable/c/d0f98a3617f6ae5b1e95cde1e68e7ead4a1279ce