CVE-2025-39964

What is 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.

Timeline

• 2025-10-13Published to the U.S. National Vulnerability Database (NVD)
• 2026-09-18Added to the CISA Known Exploited Vulnerabilities (KEV) catalog
• 2026-09-20First covered in a defend.network daily briefing
• 2026-09-21CISA federal remediation deadline (BOD 22-01)
• 2026-10-19NVD record last updated

CISA Known Exploited Vulnerability

Linux Kernel Race Condition Vulnerability

Affected product

Linux Kernel

NVD also lists CPE entries for: Linux Kernel, Siemens Simatic S7-1500 Cpu 1518-4 Pn\/Dp Mfp Firmware, Siemens Simatic S7-1500 Cpu 1518-4 Pn\/Dp Mfp, Siemens Simatic S7-1500 Cpu 1518f-4 Pn\/Dp Mfp Firmware, Siemens Simatic S7-1500 Cpu 1518f-4 Pn\/Dp Mfp

References

• https://git.kernel.org/stable/c/0f28c4adbc4a97437874c9b669fd7958a8c6d6ce
• https://git.kernel.org/stable/c/1b34cbbf4f011a121ef7b2d7d6e6920a036d5285
• https://git.kernel.org/stable/c/1f323a48e9b5ebfe6dc7d130fdf5c3c0e92a07c8
• https://nvd.nist.gov/vuln/detail/CVE-2025-39964
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog

Referenced in our briefings & reports

• Orkes Conductor RCE exploited; SolarWinds ARM patched; Linux kernel vulnerabilities added to CISA KEV (2026-09-20)

Related vulnerabilities

• CVE-2026-31431 – Linux Kernel (same product)
• CVE-2026-53362 – Linux Kernel (same product)
• CVE-2026-53266 – Linux Kernel (same product)
• CVE-2026-46300 – Linux Kernel (same product)
• CVE-2025-39682 – Linux Kernel (same product)
• CVE-2026-102489 – Zammad GmbH Zammad (same product)

Linux: 32 known exploited vulnerabilities (CISA KEV) →