CVE-2025-39964

Medium

Linux Kernel Race Condition Vulnerability

5.5 CVSS v3.1

Published: Oct 13, 2025
Updated: Oct 19, 2026
Vendor: Linux, Siemens
Affected versions: See affected products
Weakness: CWE-362

Summary

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.

Severity

Medium (5.5)

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

Linux Linux Kernel >= 2.6.38, < 5.10.245
Linux Linux Kernel >= 5.11, < 5.15.194
Linux Linux Kernel >= 5.16, < 6.1.154
Linux Linux Kernel >= 6.2, < 6.6.108
Linux Linux Kernel >= 6.7, < 6.12.49
Linux Linux Kernel >= 6.13, < 6.16.9
Linux Linux Kernel 6.17
Siemens Simatic S7-1500 Cpu 1518-4 Pn/dp Mfp Firmware >= 3.1.6
Siemens Simatic S7-1500 Cpu 1518f-4 Pn/dp Mfp Firmware >= 3.1.6

Exploitation status

Actively exploited

Listed in the CISA Known Exploited Vulnerabilities catalog on Sep 18, 2026. Federal remediation due: Sep 21, 2026.

Technical details

Technical analysis has not been written for this record yet.

Mitigation & 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.