{"id":"CVE-2021-36934","published":"2021-07-22T07:15:11Z","modified":"2026-08-10T20:19:00Z","title":"Microsoft Windows SAM Local Privilege Escalation Vulnerability","vendor":"Microsoft","product":"Windows","tier":"core","eol":null,"description":{"text":"An elevation of privilege vulnerability exists because of overly permissive Access Control Lists (ACLs) on multiple system files, including the Security Accounts Manager (SAM) database. An attacker who successfully exploited this vulnerability could run arbitrary code with SYSTEM privileges. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.\nAn attacker must have the ability to execute code on a victim system to exploit this vulnerability.\nAfter installing this security update, you must manually delete all shadow copies of system files, including the SAM database, to fully mitigate this vulnerabilty. Simply installing this security update will not fully mitigate this vulnerability. See KB5005357- Delete Volume Shadow Copies.","provenance":"source","from":"NVD"},"summary":{"text":"A flaw in Microsoft Windows caused by overly permissive access control lists on multiple system files, including the Security Accounts Manager (SAM) database, allows privilege escalation. An attacker who can already execute code on the victim system and has low-privileged access can run arbitrary code with SYSTEM privileges, giving them the ability to install programs, view, change or delete data, and create accounts with full user rights, and the fix also requires manually deleting existing shadow copies of system files, since installing the update alone does not fully mitigate it.","provenance":"ai","model":"claude-haiku-5-5","generatedAt":"2026-10-23T07:10:49Z"},"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":0.67252,"percentile":0.993,"date":"2026-10-29","provenance":"source"},"kev":{"dateAdded":"2022-02-10","dueDate":"2022-02-24","ransomware":false,"requiredAction":"Apply updates per vendor instructions.","notes":"https://nvd.nist.gov/vuln/detail/CVE-2021-36934","provenance":"source"},"vulncheckKev":{"dateAdded":"2022-02-09","exploitedFirstSeen":"2022-02-09","ransomware":false,"evidence":[{"url":"https://www.welivesecurity.com/wp-content/uploads/2022/02/eset_threat_report_t32021.pdf","date":"2022-02-09"},{"url":"https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json","date":"2022-02-10"},{"url":"https://asec.ahnlab.com/en/38156/","date":"2022-09-01"},{"url":"https://www.group-ib.com/resources/research-hub/sidewinder-apt/","date":"2023-02-14"},{"url":"https://redalert.nshc.net/2024/03/19/activity-of-hacking-group-targeted-financial-industry-in-2023-kor/","date":"2024-03-19"},{"url":"https://redalert.nshc.net/2024/04/12/activity-of-hacking-group-targeted-financial-industry-in-2023-eng/","date":"2024-04-12"}],"evidenceTotal":6,"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":[{"id":"CWE-1220","name":"Insufficient Granularity of Access Control"}],"references":[{"url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-36934","tags":["Patch","Vendor Advisory"]},{"url":"http://packetstormsecurity.com/files/164006/HiveNightmare-AKA-SeriousSAM.html","tags":["Third Party Advisory","VDB Entry"]},{"url":"https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-36934","tags":["Patch","Vendor Advisory"]},{"url":"https://www.kb.cert.org/vuls/id/506989","tags":["Third Party Advisory"]},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-36934","tags":["US Government Resource"]}],"techniques":[{"id":"T1078","name":"Valid Accounts","tactics":["initial-access","persistence","privilege-escalation","stealth"],"provenance":"source","basis":"ctid-kev","bases":["ctid-kev"],"basisDetail":"CTID Mappings Explorer KEV 07/28/2025 (ATT&CK 16.1); capability: Privilege Escalation","mappingType":"exploitation_technique","evidence":[],"comment":"This vulnerability is exploited by a local or remote adversary who already has access to the system. The vulnerability enables the attacker to elevate their privileges due to over permissive ACLs on system file and elevate their privileges to SYSTEM level. By exploiting this vulnerability an attacker could gain the ability to run arbitrary code, install programs, view/modify/delete data, or create new user accounts with full rights. ","confidence":"high"},{"id":"T1068","name":"Exploitation for Privilege Escalation","tactics":["privilege-escalation"],"provenance":"source","basis":"ctid-kev","bases":["ctid-kev"],"basisDetail":"CTID Mappings Explorer KEV 07/28/2025 (ATT&CK 16.1); capability: Privilege Escalation","mappingType":"primary_impact","evidence":[],"comment":"This vulnerability is exploited by a local or remote adversary who already has access to the system. The vulnerability enables the attacker to elevate their privileges due to over permissive ACLs on system file and elevate their privileges to SYSTEM level. By exploiting this vulnerability an attacker could gain the ability to run arbitrary code, install programs, view/modify/delete data, or create new user accounts with full rights. ","confidence":"high"}],"reports":[],"affected":[],"advisories":[],"euvd":{"id":"EUVD-2021-23510","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2021-23510","exploited":true,"exploitedSince":"2022-02-10","provenance":"source"},"exploits":[],"exploitSources":{"pocGithub":{"count":23,"skipped":1,"earliest":"2021-07-20","earliestUrl":"https://github.com/HuskyHacks/ShadowSteal","repos":[{"name":"HuskyHacks/ShadowSteal","url":"https://github.com/HuskyHacks/ShadowSteal","stars":208,"created":"2021-07-20"},{"name":"WiredPulse/Invoke-HiveNightmare","url":"https://github.com/WiredPulse/Invoke-HiveNightmare","stars":35,"created":"2021-07-22"},{"name":"JoranSlingerland/CVE-2021-36934","url":"https://github.com/JoranSlingerland/CVE-2021-36934","stars":9,"created":"2021-07-21"},{"name":"romarroca/SeriousSam","url":"https://github.com/romarroca/SeriousSam","stars":9,"created":"2021-07-22"},{"name":"Wh04m1001/VSSCopy","url":"https://github.com/Wh04m1001/VSSCopy","stars":8,"created":"2021-07-22"}]},"metasploit":[{"name":"Windows SAM secrets leak - HiveNightmare","module":"post/windows/gather/credentials/windows_sam_hivenightmare","type":"post","disclosureDate":"2021-07-20","url":"https://github.com/rapid7/metasploit-framework/blob/master/modules/post/windows/gather/credentials/windows_sam_hivenightmare.rb"}],"first":{"date":"2021-07-20","source":"PoC-in-GitHub","url":"https://github.com/HuskyHacks/ShadowSteal"},"provenance":"source"},"detections":{"cveRules":[{"title":"HackTool - Typical HiveNightmare SAM File Export","id":"6ea858a8-ba71-4a12-b2cc-5d83312404c7","level":"high","status":"test","path":"rules/windows/file/file_event/file_event_win_hktl_hivenightmare_file_exports.yml","url":"https://github.com/SigmaHQ/sigma/blob/master/rules/windows/file/file_event/file_event_win_hktl_hivenightmare_file_exports.yml","techniques":["T1552.001"]}]},"exploitRefs":["http://packetstormsecurity.com/files/164006/HiveNightmare-AKA-SeriousSAM.html"],"flow":[{"stage":"exploitation","techniques":["T1078"],"provenance":"source"},{"stage":"primary","techniques":["T1068"],"provenance":"source"}],"timeline":[{"date":"2021-07-20","kind":"exploit-public","label":"First public exploit: PoC-in-GitHub; later: Metasploit 2021-07-20","url":"https://github.com/HuskyHacks/ShadowSteal","provenance":"source"},{"date":"2021-07-22","kind":"published","label":"Published (NVD)","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-36934","provenance":"source"},{"date":"2022-02-09","kind":"exploited-reported","label":"Exploitation first reported (VulnCheck KEV evidence)","url":"https://www.welivesecurity.com/wp-content/uploads/2022/02/eset_threat_report_t32021.pdf","provenance":"source"},{"date":"2022-02-10","kind":"kev","label":"Added to CISA KEV","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","provenance":"source"},{"date":"2022-02-10","kind":"euvd-exploited","label":"ENISA EUVD: exploited","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2021-23510","provenance":"source"}],"speed":{"daysToPublicExploit":null,"firstExploitFrom":"PoC-in-GitHub","daysToKev":203},"priority":{"score":68.3,"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 1723 days ago"},{"name":"Known ransomware use","points":0.0,"detail":"not known"},{"name":"EPSS percentile","points":19.86,"detail":"percentile 0.9930"},{"name":"Named in threat reports","points":0.0,"detail":"0 reports"},{"name":"Public exploit code","points":5.0,"detail":"1 NVD exploit link; 23 PoC-in-GitHub repos; 1 Metasploit module"},{"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"}]}}