CVE-2026-72347: netfilter: xt_connmark: reject invalid shift parameters

CVE-2026-72347: netfilter: xt_connmark: reject invalid shift parameters

[Greg Kroah-Hartman]

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

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

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

netfilter: xt_connmark: reject invalid shift parameters

Revision 2 of the CONNMARK target accepts user-controlled shift
parameters and applies them to 32-bit mark values in
connmark_tg_shift().

A shift_bits value of 32 or more triggers an undefined-shift bug when
the rule is evaluated. Invalid shift_dir values are also accepted and
silently fall back to the left-shift path.

Reject invalid revision-2 shift parameters in connmark_tg_check() so
malformed rules fail at installation time, before they can reach the
packet path.

The Linux kernel CVE team has assigned CVE-2026-72347 to this issue.


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

	Issue introduced in 4.17 with commit 472a73e00757b971d613d796374d2727b2e4954d and fixed in 5.15.212 with commit d8ce63d928b457fba7ed1e302492dfd32293671c
	Issue introduced in 4.17 with commit 472a73e00757b971d613d796374d2727b2e4954d and fixed in 6.1.178 with commit 9657bb11a6376ab0a79f05d433713d6944111e9d
	Issue introduced in 4.17 with commit 472a73e00757b971d613d796374d2727b2e4954d and fixed in 6.6.145 with commit 8ace320ac4416f5e5fbcd065309fb2dfcce787b0
	Issue introduced in 4.17 with commit 472a73e00757b971d613d796374d2727b2e4954d and fixed in 6.12.97 with commit c3fa852d117b3fda72265e4230e3967db4a74fcf
	Issue introduced in 4.17 with commit 472a73e00757b971d613d796374d2727b2e4954d and fixed in 6.18.40 with commit 4eef84b09a3836919360c4232b0f16651a155eec
	Issue introduced in 4.17 with commit 472a73e00757b971d613d796374d2727b2e4954d and fixed in 7.1.5 with commit 230173cc6105bdfb2696d37e6e56687b003fbe63
	Issue introduced in 4.17 with commit 472a73e00757b971d613d796374d2727b2e4954d and fixed in 7.2-rc3 with commit 1b47026fb4b35bac850ad6e8a4ad7fc018e09ebc

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-2026-72347
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/xt_connmark.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/d8ce63d928b457fba7ed1e302492dfd32293671c
	https://git.kernel.org/stable/c/9657bb11a6376ab0a79f05d433713d6944111e9d
	https://git.kernel.org/stable/c/8ace320ac4416f5e5fbcd065309fb2dfcce787b0
	https://git.kernel.org/stable/c/c3fa852d117b3fda72265e4230e3967db4a74fcf
	https://git.kernel.org/stable/c/4eef84b09a3836919360c4232b0f16651a155eec
	https://git.kernel.org/stable/c/230173cc6105bdfb2696d37e6e56687b003fbe63
	https://git.kernel.org/stable/c/1b47026fb4b35bac850ad6e8a4ad7fc018e09ebc