{"id":"CVE-2021-43226","published":"2021-12-15T15:15:09Z","modified":"2026-08-22T04:16:54Z","title":"Microsoft Windows Privilege Escalation Vulnerability","vendor":"Microsoft","product":"Windows","tier":"core","eol":null,"description":{"text":"Windows Common Log File System Driver Elevation of Privilege Vulnerability","provenance":"source","from":"NVD"},"summary":{"text":"The flaw lies in the Common Log File System (CLFS) driver, a component of Microsoft Windows. An attacker who already has local access and a low-privilege account can exploit it to elevate their privileges, requiring no user interaction.","provenance":"ai","model":"claude-haiku-5-5","generatedAt":"2026-10-23T07:08:17Z"},"cvss":{"score":7.8,"severity":"HIGH","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","provenance":"source","from":"NVD"},"epss":{"score":0.03275,"percentile":0.8839,"date":"2026-10-29","provenance":"source"},"kev":{"dateAdded":"2025-10-06","dueDate":"2025-10-27","ransomware":true,"requiredAction":"Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.","notes":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-43226 ; https://nvd.nist.gov/vuln/detail/CVE-2021-43226","provenance":"source"},"vulncheckKev":{"dateAdded":"2022-06-13","exploitedFirstSeen":"2022-06-13","ransomware":true,"evidence":[{"url":"https://mp.weixin.qq.com/s?__biz=Mzg2NjgzNjA5NQ==&mid=2247514973&idx=2&sn=0776f8f83c032c4d7433a567270a7ee1&source=41#wechat_redirect","date":"2022-06-13"},{"url":"https://cloud.google.com/blog/topics/threat-intelligence/ransomware-attacks-surge-rely-on-public-legitimate-tools","date":"2024-06-03"},{"url":"https://www.cisa.gov/sites/default/files/2024-07/aa24-207a-dprk-cyber-group-conducts-global-espionage-campaign.pdf","date":"2024-07-25"},{"url":"https://ctrlaltint3l.github.io/threat%20research/china-vietnam-campaign/","date":"2025-08-20"},{"url":"https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json","date":"2025-10-06"},{"url":"https://cyble.com/blog/ransomware-attacks-surge-october-2025/","date":"2025-11-13"},{"url":"https://www.loginsoft.com/reports/annually/vulnerability-intelligence-report-2025","date":"2026-01-20"}],"evidenceTotal":7,"provenance":"source"},"exploited":true,"otx":{"pulseCount":50,"pulses":[{"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":"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"},{"name":"Actively_Exploited_Kev | Oct 19, 2026","url":"https://otx.alienvault.com/pulse/6ad4dda174e5797d0bd238b7","created":"2026-10-18"},{"name":"Actively_Exploited_Kev | Oct 18, 2026","url":"https://otx.alienvault.com/pulse/6ad38c22e1848f8189d1c121","created":"2026-10-17"}],"provenance":"machine"},"cwes":[],"references":[{"url":"https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43226","tags":["Patch","Vendor Advisory"]},{"url":"https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43226","tags":["Patch","Vendor Advisory"]},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-43226","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 privilege escalation via kernel driver flaw","mappingType":"exploitation_technique","evidence":[{"from":"description","quote":"Windows Common Log File System Driver Elevation of Privilege Vulnerability","start":0,"end":74}],"model":"claude-haiku-5-5","confidence":"medium","confidenceNote":"AI-mapped from the description (quote-validated, not expert-reviewed)"}],"reports":[],"affected":[],"advisories":[],"euvd":{"id":"EUVD-2021-30170","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2021-30170","exploited":true,"exploitedSince":"2025-10-06","provenance":"source"},"exploits":[],"exploitSources":{"pocGithub":{"count":1,"skipped":0,"earliest":"2023-10-30","earliestUrl":"https://github.com/Rosayxy/cve-2021-43226PoC","repos":[{"name":"Rosayxy/cve-2021-43226PoC","url":"https://github.com/Rosayxy/cve-2021-43226PoC","stars":2,"created":"2023-10-30"}]},"first":{"date":"2023-10-30","source":"PoC-in-GitHub","url":"https://github.com/Rosayxy/cve-2021-43226PoC"},"provenance":"source"},"exploitRefs":[],"flow":[{"stage":"exploitation","techniques":["T1068"],"provenance":"ai"}],"timeline":[{"date":"2021-12-15","kind":"published","label":"Published (NVD)","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-43226","provenance":"source"},{"date":"2022-06-13","kind":"exploited-reported","label":"Exploitation first reported (VulnCheck KEV evidence)","url":"https://mp.weixin.qq.com/s?__biz=Mzg2NjgzNjA5NQ==&mid=2247514973&idx=2&sn=0776f8f83c032c4d7433a567270a7ee1&source=41#wechat_redirect","provenance":"source"},{"date":"2023-10-30","kind":"exploit-public","label":"First public exploit: PoC-in-GitHub","url":"https://github.com/Rosayxy/cve-2021-43226PoC","provenance":"source"},{"date":"2025-10-06","kind":"kev","label":"Added to CISA KEV (known ransomware use)","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","provenance":"source"},{"date":"2025-10-06","kind":"euvd-exploited","label":"ENISA EUVD: exploited","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2021-30170","provenance":"source"}],"speed":{"daysToPublicExploit":684,"firstExploitFrom":"PoC-in-GitHub","daysToKev":1391},"priority":{"score":76.1,"factors":[{"name":"In a KEV catalog","points":35.0,"detail":"listed in CISA KEV and VulnCheck KEV"},{"name":"Recent KEV listing","points":0.0,"detail":"added 1599 days ago"},{"name":"Known ransomware use","points":10.0,"detail":"CISA KEV and VulnCheck KEV: Known"},{"name":"EPSS percentile","points":17.68,"detail":"percentile 0.8839"},{"name":"Named in threat reports","points":0.0,"detail":"0 reports"},{"name":"Public exploit code","points":5.0,"detail":"1 PoC-in-GitHub repo"},{"name":"Mentioned in OTX pulses","points":3.0,"detail":"50 pulses"},{"name":"CVSS severity","points":5.46,"detail":"base score 7.8"},{"name":"End-of-life product","points":0.0,"detail":"supported or unknown"}]}}