Linux Kernel Race Condition Vulnerability

Are you affected?

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• cpe linux/linux kernel6.17
• cpe siemens/simatic s7-1500 cpu 1518-4 pn/dp mfp firmwareversion unspecified
• cpe siemens/simatic s7-1500 cpu 1518f-4 pn/dp mfp firmwareversion unspecified
• vendor Linux Kernelversion unspecified

How to fix CVE-2025-39964

• Recommended remediation

  Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines. CISA due date Sep 21, 2026.

• Official advisories

  • CISA KEV · cisa.gov
  • CVE.org · cve.org
  • FIRST EPSS · first.org
  • NIST NVD · nvd.nist.gov
  • VulnCheck KEV · vulncheck.com

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Code

The project this record applies to. Exploit listings stay in References.

• Repository · git.kernel.org
• Repository · git.kernel.org
• Repository · git.kernel.org
• Repository · git.kernel.org
• Repository · git.kernel.org
• Repository · git.kernel.org
• Repository · git.kernel.org

Timeline

Detection, updates, and resolution for this record.

1. Oct 13, 2025 · Catalog

   Detected

   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 excl

2. Sep 18, 2026 · CISA KEV

   Known exploited

   Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating

3. Sep 18, 2026 · Catalog

   Updated

   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 excl

4. Sep 21, 2026 · CISA KEV

   Remediation due

   Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating

5. Oct 15, 2026 · NIST NVD

   Updated

   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 excl

6. Oct 15, 2026 · NIST NVD

   Updated

   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 excl

Sources

• CISA KEVConfirmed exploitationCVE-2025-39964

  Linux Kernel contains a race condition vulnerability which allows concurrent writes to the same AF_ALG socket causing data to be unpredictably interleaved and creating inconsistencies in the socket's internal state.

  cisa.gov
• CVE.orgVulnerability recordCVE-2025-39964

  Official CVE identifier

  cve.org
• FIRST EPSSExploitation probabilityCVE-2025-39964

  30-day exploitation probability 1.4%

  first.org
• NIST NVDVulnerability recordCVE-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 m

  nvd.nist.gov
• VulnCheck KEVConfirmed exploitationCVE-2025-39964

  Linux Kernel contains a race condition vulnerability which allows concurrent writes to the same AF_ALG socket causing data to be unpredictably interleaved and creating inconsistencies in the socket's internal state.

  vulncheck.com

References

• Third Party Advisory · cert-portal.siemens.com
• CISA note · git.kernel.org
• Patch · git.kernel.org
• CISA note · git.kernel.org
• CISA note · git.kernel.org
• CISA note · git.kernel.org
• CISA note · git.kernel.org
• CISA note · git.kernel.org
• VulnCheck exploitation evidence · cisa.gov

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.