CVE-2026-98241: ipv6: xfrm: use full sockets in local error paths

CVE-2026-98241: ipv6: xfrm: use full sockets in local error paths

[Greg Kroah-Hartman]

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

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

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

ipv6: xfrm: use full sockets in local error paths

xfrm6_local_rxpmtu() and xfrm6_local_error() dereference skb->sk as if it
always pointed at a full IPv6 socket.

That is not guaranteed. TCP SYN-ACK skbs can be owned by a
TCP_NEW_SYN_RECV request_sock while the output path itself is driven by the
full listener. If rerouting selects an IPv6 XFRM tunnel route with a lower
MTU, the local PMTU/error handling path can reach these callbacks with that
mini-socket still attached to the skb.

The callbacks then miscast the request socket as a full inet/IPv6 socket and
can read beyond the request_sock allocation when they access inet_sock or
ipv6_pinfo state.

Resolve the owner with skb_to_full_sk() in both callbacks and bail out when
no full socket is attached. This matches the surrounding XFRM IPv6 PMTU/error
logic, which already reasons about full sockets with skb_to_full_sk().

The Linux kernel CVE team has assigned CVE-2026-98241 to this issue.


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

	Issue introduced in 3.2 with commit dd767856a36e00b631d65ebc4bb81b19915532d6 and fixed in 5.10.271 with commit b1a88633c36d2cbc3831382f3846754d344276fd
	Issue introduced in 3.2 with commit dd767856a36e00b631d65ebc4bb81b19915532d6 and fixed in 5.15.222 with commit 904a0e827d0d7189271a3a2eb648293809f25efc
	Issue introduced in 3.2 with commit dd767856a36e00b631d65ebc4bb81b19915532d6 and fixed in 6.1.189 with commit 675919e08ce266b8cac11fd9af29170e762a480f
	Issue introduced in 3.2 with commit dd767856a36e00b631d65ebc4bb81b19915532d6 and fixed in 6.6.158 with commit 60459c670329d586a58db5d8f811fa5accfe4862
	Issue introduced in 3.2 with commit dd767856a36e00b631d65ebc4bb81b19915532d6 and fixed in 6.12.112 with commit ca3d68c3213475b53db6647e159dc73bd1af5ab1
	Issue introduced in 3.2 with commit dd767856a36e00b631d65ebc4bb81b19915532d6 and fixed in 6.18.54 with commit 4c030a0400ebfd2318361c923a88103b2c67c49f
	Issue introduced in 3.2 with commit dd767856a36e00b631d65ebc4bb81b19915532d6 and fixed in 7.2.8 with commit c21f3f7fbfeda7c5794f606cb0ffcc2d9001eef8
	Issue introduced in 3.2 with commit dd767856a36e00b631d65ebc4bb81b19915532d6 and fixed in 7.3-rc4 with commit 6973a21ee73c5567f883813c8ef414774b45892f

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-2026-98241
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/ipv6/xfrm6_output.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/b1a88633c36d2cbc3831382f3846754d344276fd
	https://git.kernel.org/stable/c/904a0e827d0d7189271a3a2eb648293809f25efc
	https://git.kernel.org/stable/c/675919e08ce266b8cac11fd9af29170e762a480f
	https://git.kernel.org/stable/c/60459c670329d586a58db5d8f811fa5accfe4862
	https://git.kernel.org/stable/c/ca3d68c3213475b53db6647e159dc73bd1af5ab1
	https://git.kernel.org/stable/c/4c030a0400ebfd2318361c923a88103b2c67c49f
	https://git.kernel.org/stable/c/c21f3f7fbfeda7c5794f606cb0ffcc2d9001eef8
	https://git.kernel.org/stable/c/6973a21ee73c5567f883813c8ef414774b45892f