{"id":"CVE-2025-39964","published":"2025-10-13T14:15:34Z","modified":"2026-10-19T21:10:00Z","title":"Linux Kernel Race Condition Vulnerability","vendor":"Linux","product":"Kernel","tier":"core","eol":null,"description":{"text":"In the Linux kernel, the following vulnerability has been resolved:\n\ncrypto: af_alg - Disallow concurrent writes in af_alg_sendmsg\n\nIssuing two writes to the same af_alg socket is bogus as the\ndata will be interleaved in an unpredictable fashion.  Furthermore,\nconcurrent writes may create inconsistencies in the internal\nsocket state.\n\nDisallow this by adding a new ctx->write field that indiciates\nexclusive ownership for writing.","provenance":"source","from":"NVD"},"summary":{"text":"The Linux kernel's af_alg crypto socket interface (crypto subsystem) fails to prevent concurrent writes to the same socket in af_alg_sendmsg, a race condition that can interleave data unpredictably and corrupt internal socket state. An attacker with local access and low privileges, with no user interaction needed and no special configuration indicated, could trigger the race by issuing simultaneous writes to the same socket, causing a denial of service.","provenance":"ai","model":"claude-haiku-5-5","generatedAt":"2026-10-30T13:35:44Z"},"cvss":{"score":5.5,"severity":"MEDIUM","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","provenance":"source","from":"NVD"},"epss":{"score":0.0157,"percentile":0.75309,"date":"2026-10-29","provenance":"source"},"kev":{"dateAdded":"2026-09-18","dueDate":"2026-09-21","ransomware":false,"requiredAction":"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.","notes":"This vulnerability affects an open-source component, third-party library, protocol, or proprietary implementation that could be used by different products. For more information, please see: ; 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 ; BOD 26-04: https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk ; Forensics Triage Requirements: 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","provenance":"source"},"vulncheckKev":{"dateAdded":"2026-09-18","exploitedFirstSeen":"2026-09-18","ransomware":false,"evidence":[{"url":"https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json","date":"2026-09-18"}],"evidenceTotal":1,"provenance":"source"},"exploited":true,"otx":{"pulseCount":31,"pulses":[{"name":"Actively_Exploited_Kev | Oct 30, 2026","url":"https://otx.alienvault.com/pulse/6ae35d889ea92b4ce19c2680","created":"2026-10-29"},{"name":"Actively_Exploited_Kev | Oct 29, 2026","url":"https://otx.alienvault.com/pulse/6ae20c1db17e7057ae7d9ad1","created":"2026-10-28"},{"name":"Actively_Exploited_Kev | Oct 28, 2026","url":"https://otx.alienvault.com/pulse/6ae0ba7e0e2a97ff7b218819","created":"2026-10-27"},{"name":"Actively_Exploited_Kev | Oct 27, 2026","url":"https://otx.alienvault.com/pulse/6adf68b85c3e852f3c111d18","created":"2026-10-26"},{"name":"Actively_Exploited_Kev | Oct 24, 2026","url":"https://otx.alienvault.com/pulse/6adb740e397c3ad4799aa4cd","created":"2026-10-23"},{"name":"Actively_Exploited_Kev | Oct 23, 2026","url":"https://otx.alienvault.com/pulse/6ada236fcfba2dfa730ea482","created":"2026-10-22"},{"name":"Actively_Exploited_Kev | Oct 22, 2026","url":"https://otx.alienvault.com/pulse/6ad8d33a077cbb5cab524d80","created":"2026-10-21"},{"name":"PyPI Becomes a Distribution Channel for Crimeware: The Case of 'saeka,' a Carding Automation Tool.","url":"https://otx.alienvault.com/pulse/6ad7cd3ea852b96a1ec71460","created":"2026-10-20"},{"name":"Actively_Exploited_Kev | Oct 21, 2026","url":"https://otx.alienvault.com/pulse/6ad78130c4d1ac2be83a8b6d","created":"2026-10-20"},{"name":"Actively_Exploited_Kev | Oct 20, 2026","url":"https://otx.alienvault.com/pulse/6ad62f63c24a405a3423cc13","created":"2026-10-19"}],"provenance":"machine"},"cwes":[{"id":"CWE-362","name":"Concurrent Execution using Shared Resource with Improper Synchronization"}],"references":[{"url":"https://git.kernel.org/stable/c/0f28c4adbc4a97437874c9b669fd7958a8c6d6ce","tags":["Patch"]},{"url":"https://git.kernel.org/stable/c/1b34cbbf4f011a121ef7b2d7d6e6920a036d5285","tags":["Patch"]},{"url":"https://git.kernel.org/stable/c/1f323a48e9b5ebfe6dc7d130fdf5c3c0e92a07c8","tags":["Patch"]},{"url":"https://git.kernel.org/stable/c/45bcf60fe49b37daab1acee57b27211ad1574042","tags":["Patch"]},{"url":"https://git.kernel.org/stable/c/7c4491b5644e3a3708f3dbd7591be0a570135b84","tags":["Patch"]},{"url":"https://git.kernel.org/stable/c/9aee87da5572b3a14075f501752e209801160d3d","tags":["Patch"]},{"url":"https://git.kernel.org/stable/c/e4c1ec11132ec466f7362a95f36a506ce4dc08c9","tags":["Patch"]},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-019113.html","tags":["Third Party Advisory"]},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-457936.html","tags":["Third Party Advisory"]},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-39964","tags":["US Government Resource"]}],"techniques":[{"id":"T1068","name":"Exploitation for Privilege Escalation","tactics":["privilege-escalation"],"provenance":"ai","basis":"ai-mapping","bases":["ai-mapping"],"basisDetail":"claude-haiku-5-5: local kernel bug requires privilege escalation exploitation","mappingType":"exploitation_technique","evidence":[{"from":"description","quote":"Issuing two writes to the same af_alg socket is bogus","start":132,"end":185}],"model":"claude-haiku-5-5","confidence":"medium","confidenceNote":"AI-mapped from the description (quote-validated, not expert-reviewed)"},{"id":"T1499.004","name":"Application or System Exploitation","tactics":["impact"],"provenance":"ai","basis":"ai-mapping","bases":["ai-mapping"],"basisDetail":"claude-haiku-5-5: socket state corruption causes availability impact","mappingType":"primary_impact","evidence":[{"from":"description","quote":"concurrent writes may create inconsistencies in the internal","start":261,"end":321}],"model":"claude-haiku-5-5","confidence":"medium","confidenceNote":"AI-mapped from the description (quote-validated, not expert-reviewed)"}],"reports":[],"affected":[],"advisories":[],"euvd":{"id":"EUVD-2025-34068","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2025-34068","exploited":true,"exploitedSince":"2026-09-18","provenance":"source"},"exploits":[],"exploitSources":{"pocGithub":{"count":2,"skipped":0,"earliest":"2025-11-13","earliestUrl":"https://github.com/n1k0oowang/CVE-2025-39964_EXP","repos":[{"name":"n1k0oowang/CVE-2025-39964_EXP","url":"https://github.com/n1k0oowang/CVE-2025-39964_EXP","stars":3,"created":"2025-11-13"},{"name":"suominen/CVE-2025-39964","url":"https://github.com/suominen/CVE-2025-39964","stars":0,"created":"2026-09-20"}]},"first":{"date":"2025-11-13","source":"PoC-in-GitHub","url":"https://github.com/n1k0oowang/CVE-2025-39964_EXP"},"provenance":"source"},"exploitRefs":[],"flow":[{"stage":"exploitation","techniques":["T1068"],"provenance":"ai"},{"stage":"primary","techniques":["T1499.004"],"provenance":"ai"}],"timeline":[{"date":"2025-10-13","kind":"published","label":"Published (NVD)","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-39964","provenance":"source"},{"date":"2025-11-13","kind":"exploit-public","label":"First public exploit: PoC-in-GitHub","url":"https://github.com/n1k0oowang/CVE-2025-39964_EXP","provenance":"source"},{"date":"2026-09-18","kind":"exploited-reported","label":"Exploitation first reported (VulnCheck KEV evidence)","url":"https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json","provenance":"source"},{"date":"2026-09-18","kind":"kev","label":"Added to CISA KEV","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","provenance":"source"},{"date":"2026-09-18","kind":"euvd-exploited","label":"ENISA EUVD: exploited","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2025-34068","provenance":"source"}],"speed":{"daysToPublicExploit":31,"firstExploitFrom":"PoC-in-GitHub","daysToKev":340},"priority":{"score":71.9,"factors":[{"name":"In a KEV catalog","points":35.0,"detail":"listed in CISA KEV and VulnCheck KEV"},{"name":"Recent KEV listing","points":10.0,"detail":"added 42 days ago"},{"name":"Known ransomware use","points":0.0,"detail":"not known"},{"name":"EPSS percentile","points":15.06,"detail":"percentile 0.7531"},{"name":"Named in threat reports","points":0.0,"detail":"0 reports"},{"name":"Public exploit code","points":5.0,"detail":"2 PoC-in-GitHub repos"},{"name":"Mentioned in OTX pulses","points":3.0,"detail":"31 pulses"},{"name":"CVSS severity","points":3.85,"detail":"base score 5.5"},{"name":"End-of-life product","points":0.0,"detail":"supported or unknown"}]},"lineage":{"familyId":"fam-class-linux-kernel-cwe-362"}}