linux-cve-announce - CVE-2025-40158: ipv6: use RCU in ip6

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Message-ID: <2025111258-CVE-2025-40158-4c9d@gregkh>
Date: Wed, 12 Nov 2025 19:24:34 +0900
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-40158: ipv6: use RCU in ip6_output()

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

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

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

ipv6: use RCU in ip6_output()

Use RCU in ip6_output() in order to use dst_dev_rcu() to prevent
possible UAF.

We can remove rcu_read_lock()/rcu_read_unlock() pairs
from ip6_finish_output2().

The Linux kernel CVE team has assigned CVE-2025-40158 to this issue.


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

	Issue introduced in 4.13 with commit 4a6ce2b6f2ecabbddcfe47e7cf61dd0f00b10e36 and fixed in 6.17.3 with commit 0393f85c3241c19ba8550f04a812e7d19f6b3082
	Issue introduced in 4.13 with commit 4a6ce2b6f2ecabbddcfe47e7cf61dd0f00b10e36 and fixed in 6.18-rc1 with commit 11709573cc4e48dc34c80fc7ab9ce5b159e29695

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-2025-40158
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/ip6_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/0393f85c3241c19ba8550f04a812e7d19f6b3082
	https://git.kernel.org/stable/c/11709573cc4e48dc34c80fc7ab9ce5b159e29695