# CVE-2025-39964

In the Linux kernel, the following vulnerability has been resolved: crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg Issuing two writes to the same af_alg socket is bogus as the data will be interleaved in an unpredictable fashion. Furthermore, concurrent writes may create inconsistencies in the internal socket state. Disallow this by adding a new ctx->write field that indiciates exclusive ownership for writing.

- Page: https://www.vulneraibility.com/cve/CVE-2025-39964
- CVSS: 7.8
- Known exploited: yes, in CISA KEV since 2026-09-18; CISA due date 2026-09-21
- EPSS: 1.61%
- Unvetted proof-of-concept code on GitHub: 2 GitHub proofs of concept (first 2025-11-13)
- CISA SSVC: exploitation active, automatable no, technical impact total (assessed 2026-09-18)
- Weakness: CWE-362
- Published: 2025-10-13

## Affected versions

- Linux: affected >= 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and < 0f28c4adbc4a97437874c9b669fd7958a8c6d6ce; >= 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and < e4c1ec11132ec466f7362a95f36a506ce4dc08c9; >= 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and < 1f323a48e9b5ebfe6dc7d130fdf5c3c0e92a07c8; >= 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and < 7c4491b5644e3a3708f3dbd7591be0a570135b84; >= 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and < 9aee87da5572b3a14075f501752e209801160d3d; >= 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and < 45bcf60fe49b37daab1acee57b27211ad1574042; >= 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 and < 1b34cbbf4f011a121ef7b2d7d6e6920a036d5285; 2.6.38; fixed in < 2.6.38, >= 5.10.245 and <= 5.10.*, >= 5.15.194 and <= 5.15.*, >= 6.1.154 and <= 6.1.*, >= 6.6.108 and <= 6.6.*, >= 6.12.49 and <= 6.12.*, >= 6.16.9 and <= 6.16.*, >= 6.17 and <= *

A version outside these ranges is not a statement that it is unaffected.

## References

- [other] https://git.kernel.org/stable/c/0f28c4adbc4a97437874c9b669fd7958a8c6d6ce
- [other] https://git.kernel.org/stable/c/e4c1ec11132ec466f7362a95f36a506ce4dc08c9
- [other] https://git.kernel.org/stable/c/1f323a48e9b5ebfe6dc7d130fdf5c3c0e92a07c8
- [other] https://git.kernel.org/stable/c/7c4491b5644e3a3708f3dbd7591be0a570135b84
- [other] https://git.kernel.org/stable/c/9aee87da5572b3a14075f501752e209801160d3d
- [other] https://git.kernel.org/stable/c/45bcf60fe49b37daab1acee57b27211ad1574042
- [other] https://git.kernel.org/stable/c/1b34cbbf4f011a121ef7b2d7d6e6920a036d5285
- [other] https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-39964
- [other] https://cert-portal.siemens.com/productcert/html/ssa-019113.html
- [other] https://cert-portal.siemens.com/productcert/html/ssa-457936.html

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Summary, impact and action are written by the vulneraibility.com AI analysis pipeline from the CVE record, NVD, CISA and FIRST data; verify against the references.