CVE-2026-72253: netfilter: nf_conntrack_sip: validate skb_dst() before accessing it

CVE-2026-72253: netfilter: nf_conntrack_sip: validate skb_dst() before accessing it

[Greg Kroah-Hartman]

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

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

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

netfilter: nf_conntrack_sip: validate skb_dst() before accessing it

tc ingress and openvswitch do not guarantee routing information to be
available. These subsystems use the conntrack helper infrastructure, and
the SIP helper relies on the skb_dst() to be present if
sip_external_media is set to 1 (which is disabled by default as a module
parameter).

This effectively disables the sip_external_media toggle for these
subsystems without resulting in a crash.

The Linux kernel CVE team has assigned CVE-2026-72253 to this issue.


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

	Issue introduced in 4.3 with commit cae3a2627520c3795b54533c5328b77af3405dbe and fixed in 6.6.148 with commit e64a48c50a1ff565a98c6a98d82b5b942868e76e
	Issue introduced in 4.3 with commit cae3a2627520c3795b54533c5328b77af3405dbe and fixed in 6.12.101 with commit c199ed687c00841daf60e9d131976958583a8c09
	Issue introduced in 4.3 with commit cae3a2627520c3795b54533c5328b77af3405dbe and fixed in 6.18.42 with commit 09755dc62b026076b1d47f83489eb0547c8135e0
	Issue introduced in 4.3 with commit cae3a2627520c3795b54533c5328b77af3405dbe and fixed in 7.1.5 with commit b843a96252f672332837ea2ecb7c8db0acf68e20
	Issue introduced in 4.3 with commit cae3a2627520c3795b54533c5328b77af3405dbe and fixed in 7.2-rc2 with commit e5e24a365a5e024efef63cc49abb345fbd4852c5

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-2026-72253
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/netfilter/nf_conntrack_sip.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/e64a48c50a1ff565a98c6a98d82b5b942868e76e
	https://git.kernel.org/stable/c/c199ed687c00841daf60e9d131976958583a8c09
	https://git.kernel.org/stable/c/09755dc62b026076b1d47f83489eb0547c8135e0
	https://git.kernel.org/stable/c/b843a96252f672332837ea2ecb7c8db0acf68e20
	https://git.kernel.org/stable/c/e5e24a365a5e024efef63cc49abb345fbd4852c5