CVE-2025-39964: Linux Kernel Race Condition Vulnerability

CISA Known Exploited Vulnerabilities

Name

Linux Kernel Race Condition Vulnerability

Vendor

Linux

Product

Kernel

Added to the catalog

2026-09-18

Due date for US federal agencies

2026-09-21

Weaknesses

CWE-362

Catalog version

2026.10.30

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.

Required action (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.

Ransomware use: CISA does not mark known use of this vulnerability in ransomware campaigns.

Links in CISA's notes

• https://git.kernel.org/stable/c/0f28c4adbc4a97437874c9b669fd7958a8c6d6ce
• https://git.kernel.org/stable/c/e4c1ec11132ec466f7362a95f36a506ce4dc08c9
• https://git.kernel.org/stable/c/1f323a48e9b5ebfe6dc7d130fdf5c3c0e92a07c8
• https://git.kernel.org/stable/c/7c4491b5644e3a3708f3dbd7591be0a570135b84
• https://git.kernel.org/stable/c/9aee87da5572b3a14075f501752e209801160d3d
• https://git.kernel.org/stable/c/45bcf60fe49b37daab1acee57b27211ad1574042
• https://git.kernel.org/stable/c/1b34cbbf4f011a121ef7b2d7d6e6920a036d5285
• https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk
• https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk
• https://nvd.nist.gov/vuln/detail/CVE-2025-39964

Read on 2026-11-02T23:39:54.475Z under licence cisa-kev-cc0@b0067899 from https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json

NVD analysis

Status

Analyzed

Published

2025-10-13T14:15:34.737

Last modified

2026-10-19T21:10:00.160

Weaknesses

CWE-362

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.

References

• https://git.kernel.org/stable/c/0f28c4adbc4a97437874c9b669fd7958a8c6d6ce (Patch)
• https://git.kernel.org/stable/c/1b34cbbf4f011a121ef7b2d7d6e6920a036d5285 (Patch)
• https://git.kernel.org/stable/c/1f323a48e9b5ebfe6dc7d130fdf5c3c0e92a07c8 (Patch)
• https://git.kernel.org/stable/c/45bcf60fe49b37daab1acee57b27211ad1574042 (Patch)
• https://git.kernel.org/stable/c/7c4491b5644e3a3708f3dbd7591be0a570135b84 (Patch)
• https://git.kernel.org/stable/c/9aee87da5572b3a14075f501752e209801160d3d (Patch)
• https://git.kernel.org/stable/c/e4c1ec11132ec466f7362a95f36a506ce4dc08c9 (Patch)
• https://cert-portal.siemens.com/productcert/html/ssa-019113.html (Third Party Advisory)
• https://cert-portal.siemens.com/productcert/html/ssa-457936.html (Third Party Advisory)
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-39964 (US Government Resource)

This product uses the NVD API but is not endorsed or certified by the NVD.

Read on 2026-11-02T23:42:22.836Z under licence nvd-api-terms-of-use@ff2a5288 from https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2025-39964

CVE record

Title (CNA)

crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg

Assigner

Linux

State

PUBLISHED

Published

2025-10-13T13:48:30.334Z

Updated

2026-10-15T01:08:42.257Z

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.

References

• https://git.kernel.org/stable/c/0f28c4adbc4a97437874c9b669fd7958a8c6d6ce
• https://git.kernel.org/stable/c/e4c1ec11132ec466f7362a95f36a506ce4dc08c9
• https://git.kernel.org/stable/c/1f323a48e9b5ebfe6dc7d130fdf5c3c0e92a07c8
• https://git.kernel.org/stable/c/7c4491b5644e3a3708f3dbd7591be0a570135b84
• https://git.kernel.org/stable/c/9aee87da5572b3a14075f501752e209801160d3d
• https://git.kernel.org/stable/c/45bcf60fe49b37daab1acee57b27211ad1574042
• https://git.kernel.org/stable/c/1b34cbbf4f011a121ef7b2d7d6e6920a036d5285

Read on 2026-11-03T02:16:26.568Z under licence cve-terms-of-use@81bfa2f3 from https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2025/39xxx/CVE-2025-39964.json

Defensive techniques (MITRE D3FEND)

D3FEND maps these defensive techniques to the weakness (CWE) that NVD lists for this CVE, through the digital artifacts the weakness affects. D3FEND does not say they stop this vulnerability.

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