---
id: CVE-2025-39931
title: |-
  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
summary: |-
  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.  …
severity: medium
cvss: 5.5
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-908
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 2.6.38, < 6.1.154'
  - 'linux_kernel >= 6.2, < 6.6.108'
  - 'linux_kernel >= 6.7, < 6.12.49'
  - 'linux_kernel >= 6.13, < 6.16.9'
  - linux_kernel = 6.17
patched:
  - linux_kernel 6.16.9
published: '2025-10-04'
updated: '2026-07-04'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-39931'
references:
  - url: 'https://git.kernel.org/stable/c/045ee26aa3920a47ec46d7fcb302420bf01fd753'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/2374c11189ef704a3e4863646369f1b8e6a27d71'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/24c1106504c625fabd3b7229611af617b4c27ac7'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/28f6f37abca7c5c9eb3959c66310f1d4d98b8aaf'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/6241b9e2809b12da9130894cf5beddf088dc1b8a'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/9574b2330dbd2b5459b74d3b5e9619d39299fc6f'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/db2b42425dfbde4983b0c20fb7cfa05f70e6a745'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-082556.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
tags:
  - nvd
  - cve.org
epss: 0.00161
epssPercentile: 0.04576
ingestedAt: '2026-07-04T12:56:09.233Z'
---

## Overview

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.

## Affected

- `linux_kernel >= 2.6.38, < 6.1.154`
- `linux_kernel >= 6.2, < 6.6.108`
- `linux_kernel >= 6.7, < 6.12.49`
- `linux_kernel >= 6.13, < 6.16.9`
- `linux_kernel = 6.17`

## Remediation

Upgrade past the affected range:

- `linux_kernel 6.16.9`