CVE-2026-74724: ipvs: avoid out-of-bounds write in ip_vs_nat_icmp

From: Greg Kroah-Hartman <[email protected]>

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

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

ipvs: avoid out-of-bounds write in ip_vs_nat_icmp

Sashiko warns that local attacker can modify the packet
while it is processed by IPVS. Some places read the
IP ihl field multiple times which can cause out-of-bounds
access. One such place is ip_vs_nat_icmp where we
can write after the validated area.

Fix it by providing ciph argument just like it is done for
IPv6 and use ciph->len as offset to the embedded transport
header.

Modify some IPv4 header checks by reading the ihl field
only once.

The Linux kernel CVE team has assigned CVE-2026-74724 to this issue.


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

	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 6.1.183 with commit 3b8f79af0e98f27b932b0b416e9c52b692d31ff9
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 6.6.152 with commit 3c779b258c9c3c3567af68d4f45c2f751f35bd0e
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 6.12.104 with commit be65fa324640c7a95e30b146159a2be5cc73f22e
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 6.18.45 with commit a69a4b3fff5814d079beff9a1e9d369994b2ed47
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 7.1.9 with commit 243d0187ec4c3837b9b0004f18d1068e46115760
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 7.2 with commit 646922a0379496154e8c8faca4f8e2fd9100cacc

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-2026-74724
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:
	include/net/ip_vs.h
	net/netfilter/ipvs/ip_vs_core.c
	net/netfilter/ipvs/ip_vs_xmit.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/3b8f79af0e98f27b932b0b416e9c52b692d31ff9
	https://git.kernel.org/stable/c/3c779b258c9c3c3567af68d4f45c2f751f35bd0e
	https://git.kernel.org/stable/c/be65fa324640c7a95e30b146159a2be5cc73f22e
	https://git.kernel.org/stable/c/a69a4b3fff5814d079beff9a1e9d369994b2ed47
	https://git.kernel.org/stable/c/243d0187ec4c3837b9b0004f18d1068e46115760
	https://git.kernel.org/stable/c/646922a0379496154e8c8faca4f8e2fd9100cacc