linux-cve-announce - CVE-2026-23204: net/sched: cls_u32: use skb_header_pointer

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Message-ID: <2026021437-CVE-2026-23204-be85@gregkh>
Date: Sat, 14 Feb 2026 17:29:01 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2026-23204: net/sched: cls_u32: use skb_header_pointer_careful()

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

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

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

net/sched: cls_u32: use skb_header_pointer_careful()

skb_header_pointer() does not fully validate negative @offset values.

Use skb_header_pointer_careful() instead.

GangMin Kim provided a report and a repro fooling u32_classify():

BUG: KASAN: slab-out-of-bounds in u32_classify+0x1180/0x11b0
net/sched/cls_u32.c:221

The Linux kernel CVE team has assigned CVE-2026-23204 to this issue.


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

	Issue introduced in 2.6.35 with commit fbc2e7d9cf49e0bf89b9e91fd60a06851a855c5d and fixed in 6.6.124 with commit 13336a6239b9d7c6e61483017bb8bdfe3ceb10a5
	Issue introduced in 2.6.35 with commit fbc2e7d9cf49e0bf89b9e91fd60a06851a855c5d and fixed in 6.12.70 with commit e41a23e61259f5526af875c3b86b3d42a9bae0e5
	Issue introduced in 2.6.35 with commit fbc2e7d9cf49e0bf89b9e91fd60a06851a855c5d and fixed in 6.18.10 with commit 8a672f177ebe19c93d795fbe967846084fbc7943
	Issue introduced in 2.6.35 with commit fbc2e7d9cf49e0bf89b9e91fd60a06851a855c5d and fixed in 6.19 with commit cabd1a976375780dabab888784e356f574bbaed8

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-2026-23204
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/sched/cls_u32.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/13336a6239b9d7c6e61483017bb8bdfe3ceb10a5
	https://git.kernel.org/stable/c/e41a23e61259f5526af875c3b86b3d42a9bae0e5
	https://git.kernel.org/stable/c/8a672f177ebe19c93d795fbe967846084fbc7943
	https://git.kernel.org/stable/c/cabd1a976375780dabab888784e356f574bbaed8