linux-cve-announce - CVE-2026-23048: udp: call skb_orphan() before skb_attempt_defer

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Message-ID: <2026020441-CVE-2026-23048-f1cc@gregkh>
Date: Wed,  4 Feb 2026 17:00:48 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2026-23048: udp: call skb_orphan() before skb_attempt_defer_free()

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

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

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

udp: call skb_orphan() before skb_attempt_defer_free()

Standard UDP receive path does not use skb->destructor.

But skmsg layer does use it, since it calls skb_set_owner_sk_safe()
from udp_read_skb().

This then triggers this warning in skb_attempt_defer_free():

    DEBUG_NET_WARN_ON_ONCE(skb->destructor);

We must call skb_orphan() to fix this issue.

The Linux kernel CVE team has assigned CVE-2026-23048 to this issue.


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

	Issue introduced in 6.18 with commit 6471658dc66c670580a7616e75f51b52917e7883 and fixed in 6.18.6 with commit 0c63d5683eae6a7b4d81382bcbecb2a19feff90d
	Issue introduced in 6.18 with commit 6471658dc66c670580a7616e75f51b52917e7883 and fixed in 6.19-rc5 with commit e5c8eda39a9fc1547d1398d707aa06c1d080abdd

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-2026-23048
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/ipv4/udp.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/0c63d5683eae6a7b4d81382bcbecb2a19feff90d
	https://git.kernel.org/stable/c/e5c8eda39a9fc1547d1398d707aa06c1d080abdd