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CVE-2025-39964

HIGH
7.8 CISA KEVNVD

Summary

generated automatically from NVD data

CVE-2025-39964 is a race condition (CWE-362) in the Linux kernel's crypto af_alg interface, where af_alg_sendmsg allowed concurrent writes to the same socket. Simultaneous writes could interleave data unpredictably and leave the internal socket state inconsistent. The resolution adds a ctx->write field to give one writer exclusive ownership. It carries a CVSS v3.1 score of 7.8 (HIGH), is listed in the CISA KEV catalog, and NVD also lists certain Siemens SIMATIC S7-1500 CPU 1518 firmware as affected.

NVD 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.

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⚠️ Actively exploited — CISA KEV

This CVE was added to CISA's Known Exploited Vulnerabilities catalog on 2026-09-18. It is confirmed exploited in the wild and must be patched as a priority.

Remediation deadline (US federal agencies): 2026-09-21

EPSS · FIRST.org

1.4%probability of exploitation in the next 30 days

Higher than 71% of scored CVEs

EPSS (Exploit Prediction Scoring System) estimates, from observed exploitation activity, how likely a CVE is to be exploited in the next 30 days. It complements CVSS, which measures severity, not likelihood. Score of 2026-10-16, recomputed daily by FIRST.org.

In-depth analysis on cveo.tech

We've published a detailed analysis of this CVE — exploitation, IOCs and mitigation.

CVSS v3.1 Score

7.8
/ 10.0
HIGH
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Information

Published
13 oct. 2025
Updated
15 oct. 2026
Status
Analyzed
Source
416baaa9-dc9f-4396-8d5f-8c081fb06d67

Affected products

linux linux kernelAll Linux Kernel CVEs →
Versions : 5.10.245, 5.15.194, 6.1.154, 6.6.108, 6.12.49
siemens simatic s7-1500 cpu 1518-4 pn\/dp mfp firmware
siemens simatic s7-1500 cpu 1518f-4 pn\/dp mfp firmware

Weaknesses (CWE)

CWE-362CWE-362

References (10)

Similar CVEs

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