CVE-2025-39964

crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg

High 7.8
Exploited: added to CISA KEV 18 Sep 2026

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.

Key facts

Published: 13 Oct 2025
Last changed: 10 Nov 2026
Assigned by: Linux
KEV added: 18 Sep 2026
KEV fix due: 21 Sep 2026
EPSS: 1.607% likely to be exploited in the next 30 days, higher than 76.292% of CVEs (scores for 15 Nov 2026)
SSVC (CISA): Exploitation: active; Automatable: no; Technical impact: total

Severity scores

Each score is shown as its source gave it. They are not averaged or merged.

7.8CVSS 3.1, Highfrom the CNA (Linux)CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

What to do

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.CISA KEV required action

Historical context and remediation

This reference retains the original CVE publication date. A recent record update does not mean a new attack occurred.

No separately sourced impact summary is available on this page yet. Consult the description, version data and dated exploitation evidence.

Version statuses below come from the CNA. An “unaffected” version is not necessarily a currently supported release or proof of a patch date. EPSS is a dated risk estimate, not a count of historical attacks.

Read the original CVE record.

Affected products

Vendor	Product	Versions
Linux	Linux	Default status: unaffected 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 up to but excluding 0f28c4adbc4a97437874c9b669fd7958a8c6d6ce (affected) 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 up to but excluding e4c1ec11132ec466f7362a95f36a506ce4dc08c9 (affected) 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 up to but excluding 1f323a48e9b5ebfe6dc7d130fdf5c3c0e92a07c8 (affected) 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 up to but excluding 7c4491b5644e3a3708f3dbd7591be0a570135b84 (affected) 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 up to but excluding 9aee87da5572b3a14075f501752e209801160d3d (affected) 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 up to but excluding 45bcf60fe49b37daab1acee57b27211ad1574042 (affected) 8ff590903d5fc7f5a0a988c38267a3d08e6393a2 up to but excluding 1b34cbbf4f011a121ef7b2d7d6e6920a036d5285 (affected)
Linux	Linux	Default status: affected 2.6.38 (affected) 0 up to but excluding 2.6.38 (unaffected) 5.10.245 up to and including 5.10.* (unaffected) 5.15.194 up to and including 5.15.* (unaffected) 6.1.154 up to and including 6.1.* (unaffected) 6.6.108 up to and including 6.6.* (unaffected) 6.12.49 up to and including 6.12.* (unaffected) 6.16.9 up to and including 6.16.* (unaffected) 6.17 up to and including * (unaffected)