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CVE-2025-39964

HIGH7.8
CISA KEV

Published 2025-10-13 · Updated 2026-10-19 · Source 416baaa9-dc9f-4396-8d5f-8c081fb06d67

Summary

CVE-2025-39964 is a high-severity (CVSS 7.8) vulnerability in Linux Kernel. CISA added it to the Known Exploited Vulnerabilities catalog on September 18, 2026, which means exploitation in the wild has been confirmed; US federal agencies had to remediate it by September 21, 2026. CISA does not currently list it as used in ransomware campaigns. Linux has 32 vulnerabilities in the KEV catalog, 2 of them linked to ransomware.

All 32 known-exploited Linux vulnerabilities →

Description

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.

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

CWE-362CWE-362

CISA Known-Exploited Vulnerability

Product: Linux — Kernel

Name: Linux Kernel Race Condition Vulnerability

Date added: 2026-09-18 · Due: 2026-09-21

Required action: 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.

References

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