CVE-2025-39964

Published Oct 13, 2025

Last updated a day ago

Overview

AI description

Automated description summarized from trusted sources.

CVE-2025-39964 describes a race condition vulnerability found within the Linux kernel's cryptographic user API, specifically affecting the `AF_ALG` component. This flaw arises from the way concurrent write operations to the same `AF_ALG` socket are managed. The vulnerability can lead to unpredictable interleaving of data and inconsistencies in the internal state of the socket. To address this, a fix was implemented that introduces an exclusive write ownership mechanism (`ctx->write`), ensuring that only one writer can issue `sendmsg()` at a time and preventing state corruption.

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.
Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
NVD status: Analyzed
Products: linux_kernel, simatic_s7-1500_cpu_1518-4_pn\/dp_mfp_firmware, simatic_s7-1500_cpu_1518f-4_pn\/dp_mfp_firmware

Risk scores

CVSS 3.1

Type: Primary
Base score: 5.5
Impact score: 3.6
Exploitability score: 1.8
Vector string: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Severity: MEDIUM

Known exploits

Data from CISA

Vulnerability name: Linux Kernel Race Condition Vulnerability
Exploit added on: Sep 18, 2026
Exploit action due: Sep 21, 2026
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.

Weaknesses

nvd@nist.gov: CWE-362
134c704f-9b21-4f2e-91b3-4a467353bcc0: CWE-362

Hype score is a measure of social media activity compared against trending CVEs from the past 12 months. Max score 100.

Hype score: 19

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References

Sources include official advisories and independent security research.