linux-cve-announce - CVE-2026-23083: fou: Don't allow 0 for FOU_ATTR

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Message-ID: <2026020422-CVE-2026-23083-8968@gregkh>
Date: Wed,  4 Feb 2026 17:14:42 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2026-23083: fou: Don't allow 0 for FOU_ATTR_IPPROTO.

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

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

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

fou: Don't allow 0 for FOU_ATTR_IPPROTO.

fou_udp_recv() has the same problem mentioned in the previous
patch.

If FOU_ATTR_IPPROTO is set to 0, skb is not freed by
fou_udp_recv() nor "resubmit"-ted in ip_protocol_deliver_rcu().

Let's forbid 0 for FOU_ATTR_IPPROTO.

The Linux kernel CVE team has assigned CVE-2026-23083 to this issue.


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

	Issue introduced in 3.18 with commit 23461551c00628c3f3fe9cf837bf53cf8f212b63 and fixed in 6.6.122 with commit 1cc98b8887cabb1808d2f4a37cd10a7be7574771
	Issue introduced in 3.18 with commit 23461551c00628c3f3fe9cf837bf53cf8f212b63 and fixed in 6.12.68 with commit b7db31a52c3862a1a32202a273a4c32e7f5f4823
	Issue introduced in 3.18 with commit 23461551c00628c3f3fe9cf837bf53cf8f212b63 and fixed in 6.18.8 with commit 9b75dff8446ec871030d8daf5a69e74f5fe8b956
	Issue introduced in 3.18 with commit 23461551c00628c3f3fe9cf837bf53cf8f212b63 and fixed in 6.19-rc7 with commit 7a9bc9e3f42391e4c187e099263cf7a1c4b69ff5

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-2026-23083
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:
	Documentation/netlink/specs/fou.yaml
	net/ipv4/fou_nl.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/1cc98b8887cabb1808d2f4a37cd10a7be7574771
	https://git.kernel.org/stable/c/b7db31a52c3862a1a32202a273a4c32e7f5f4823
	https://git.kernel.org/stable/c/9b75dff8446ec871030d8daf5a69e74f5fe8b956
	https://git.kernel.org/stable/c/7a9bc9e3f42391e4c187e099263cf7a1c4b69ff5