Critical SEVERITY — Vulnerability

CVE-2025-39964 — Linux Kernel Race Condition Vulnerability

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.

Platform
Ubuntu Server
CVE Record
CVE-2025-39964
Advisory
CISA-KEV
Published
18 September 2026
Views
23
Primary source: Review the official advisory at nvd.nist.gov Go to Source

Status

This vulnerability appears in CISA's catalog of known exploited vulnerabilities. It is not a theoretical risk — it is being used in the wild.

Description

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.

Details

  • Vendor: Linux
  • Product: Kernel
  • Added to catalog: 2026-09-18

Action Required by CISA

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.

  • Due date for federal agencies: 2026-09-21
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