CVE-2026-43383: net/tcp-md5: Fix MAC comparison to be constant-time

CVE-2026-43383: net/tcp-md5: Fix MAC comparison to be constant-time

[Greg Kroah-Hartman]

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

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

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

net/tcp-md5: Fix MAC comparison to be constant-time

To prevent timing attacks, MACs need to be compared in constant
time.  Use the appropriate helper function for this.

The Linux kernel CVE team has assigned CVE-2026-43383 to this issue.


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

	Issue introduced in 2.6.20 with commit cfb6eeb4c860592edd123fdea908d23c6ad1c7dc and fixed in 5.10.253 with commit 821c8751fdeecdeecabeb11704dd33439c9e4bbc
	Issue introduced in 2.6.20 with commit cfb6eeb4c860592edd123fdea908d23c6ad1c7dc and fixed in 6.1.167 with commit 345a9530756528d7ca407663d659c3c40e75c3dd
	Issue introduced in 2.6.20 with commit cfb6eeb4c860592edd123fdea908d23c6ad1c7dc and fixed in 6.6.130 with commit 5d305a95130a8d08b9545e47f1e18d29d59866cb
	Issue introduced in 2.6.20 with commit cfb6eeb4c860592edd123fdea908d23c6ad1c7dc and fixed in 6.12.78 with commit 02669e2a4d207068edce7e8b5fafd85822018ce6
	Issue introduced in 2.6.20 with commit cfb6eeb4c860592edd123fdea908d23c6ad1c7dc and fixed in 6.18.19 with commit ae3831b44f477de048287493e184fc3ff913b624
	Issue introduced in 2.6.20 with commit cfb6eeb4c860592edd123fdea908d23c6ad1c7dc and fixed in 6.19.9 with commit b502e97e29d791ff7a8051f29a414535739be218
	Issue introduced in 2.6.20 with commit cfb6eeb4c860592edd123fdea908d23c6ad1c7dc and fixed in 7.0 with commit 46d0d6f50dab706637f4c18a470aac20a21900d3

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-2026-43383
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/Kconfig
	net/ipv4/tcp.c
	net/ipv4/tcp_ipv4.c
	net/ipv6/tcp_ipv6.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/821c8751fdeecdeecabeb11704dd33439c9e4bbc
	https://git.kernel.org/stable/c/345a9530756528d7ca407663d659c3c40e75c3dd
	https://git.kernel.org/stable/c/5d305a95130a8d08b9545e47f1e18d29d59866cb
	https://git.kernel.org/stable/c/02669e2a4d207068edce7e8b5fafd85822018ce6
	https://git.kernel.org/stable/c/ae3831b44f477de048287493e184fc3ff913b624
	https://git.kernel.org/stable/c/b502e97e29d791ff7a8051f29a414535739be218
	https://git.kernel.org/stable/c/46d0d6f50dab706637f4c18a470aac20a21900d3