linux-cve-announce - CVE-2025-39931: crypto: af_alg - Set merge to zero early in af_alg

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Message-ID: <2025100416-CVE-2025-39931-8ff7@gregkh>
Date: Sat,  4 Oct 2025 09:33:15 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-39931: crypto: af_alg - Set merge to zero early in af_alg_sendmsg

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

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

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

crypto: af_alg - Set merge to zero early in af_alg_sendmsg

If an error causes af_alg_sendmsg to abort, ctx->merge may contain
a garbage value from the previous loop.  This may then trigger a
crash on the next entry into af_alg_sendmsg when it attempts to do
a merge that can't be done.

Fix this by setting ctx->merge to zero near the start of the loop.

The Linux kernel CVE team has assigned CVE-2025-39931 to this issue.


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

	Issue introduced in 2.6.38 with commit 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and fixed in 6.1.154 with commit 6241b9e2809b12da9130894cf5beddf088dc1b8a
	Issue introduced in 2.6.38 with commit 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and fixed in 6.6.108 with commit 2374c11189ef704a3e4863646369f1b8e6a27d71
	Issue introduced in 2.6.38 with commit 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and fixed in 6.12.49 with commit 24c1106504c625fabd3b7229611af617b4c27ac7
	Issue introduced in 2.6.38 with commit 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and fixed in 6.16.9 with commit 045ee26aa3920a47ec46d7fcb302420bf01fd753
	Issue introduced in 2.6.38 with commit 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and fixed in 6.17 with commit 9574b2330dbd2b5459b74d3b5e9619d39299fc6f

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-2025-39931
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:
	crypto/af_alg.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/6241b9e2809b12da9130894cf5beddf088dc1b8a
	https://git.kernel.org/stable/c/2374c11189ef704a3e4863646369f1b8e6a27d71
	https://git.kernel.org/stable/c/24c1106504c625fabd3b7229611af617b4c27ac7
	https://git.kernel.org/stable/c/045ee26aa3920a47ec46d7fcb302420bf01fd753
	https://git.kernel.org/stable/c/9574b2330dbd2b5459b74d3b5e9619d39299fc6f