{"id":"CVE-2021-36942","kind":"vulnerability","aliases":["CVE-2021-36942"],"related":[],"title":"Microsoft Windows: Microsoft Windows Local Security Authority (LSA) Spoofing Vulnerability","description":"Microsoft Windows Local Security Authority (LSA) contains a spoofing vulnerability allowing an unauthenticated attacker to call a method on the LSARPC interface and coerce the domain controller to authenticate against another server using NTLM.\n\nCISA required action: Apply updates per vendor instructions.","summary":"A spoofing flaw in the Windows Local Security Authority lets an unauthenticated attacker call a method on the LSARPC interface and force a domain controller to authenticate to another server over NTLM. The attacker can capture or relay that NTLM authentication and impersonate the domain controller's machine account.","severity":"high","cvss":7.5,"epss":0.66023,"exploited":true,"exploited_at":"2021-11-03T00:00:00+00:00","products":[{"name":"Microsoft Windows","fixed":[],"affected":"","ecosystem":"vendor"}],"ecosystems":["vendor"],"tags":["active-directory","domain-controllers","exploited","infrastructure","ransomware","windows"],"not_affected_if":["patched-windows"],"how_to_check":null,"fix":"Apply the Microsoft update for CVE-2021-36942 per vendor instructions (CISA KEV required action).","status":"open","published_at":"2021-08-12T18:15:10+00:00","first_seen_at":"2026-10-23T19:11:53+00:00","triaged_at":"2026-10-23T21:41:19+00:00","updated_at":"2026-10-23T21:57:34+00:00","category":"infrastructure","confidence":0.6,"triage":{"at":"2026-10-23T21:41:19Z","model":"claude-haiku-5-5","output":{"fix":"Apply the Microsoft update for CVE-2021-36942 per vendor instructions (CISA KEV required action).\nunknown","reach":"network","impact":"high","summary":"A spoofing flaw in the Windows Local Security Authority lets an unauthenticated attacker call a method on the LSARPC interface and force a domain controller to authenticate to another server over NTLM. The attacker can capture or relay that NTLM authentication and impersonate the domain controller's machine account.","category":"infrastructure","who_cares":["windows","active-directory","domain-controllers"],"confidence":0.6,"needs_auth":"no","worst_case":"Attacker impersonates a domain controller and takes over domain credentials.","analyst_note":"Find the Microsoft patch KB and affected Windows builds at the MSRC entry for CVE-2021-36942 and confirm the detection command for unpatched domain controllers.","how_to_check":"unknown","needs_analyst":true,"not_affected_if":["patched-windows"],"user_interaction":"no","needs_special_setup":"unknown","severity_if_unknown":"high"},"cost_usd":0.000479,"input_tokens":2873,"output_tokens":384,"severity_before":"unknown"},"analyst_status":"queued","analyst_note":"Find the Microsoft patch KB and affected Windows builds at the MSRC entry for CVE-2021-36942 and confirm the detection command for unpatched domain controllers.","search":"'-2021':12A,15A '-36942':13A,16A 'account':77B 'action':114C 'activ':20B 'active-directori':19B 'allow':88C 'anoth':57B,108C 'appli':115C 'attack':41B,62B,91C 'authent':55B,69B,106C 'author':7A,37B,82C 'call':42B,93C 'captur':64B 'cisa':112C 'coerc':101C 'contain':84C 'control':24B,53B,74B,104C 'cve':11A,14A 'directori':21B 'domain':23B,52B,73B,103C 'domain-control':22B 'exploit':25B 'flaw':31B 'forc':50B 'imperson':71B 'infrastructur':26B 'instruct':119C 'interfac':48B,99C 'let':38B 'local':5A,35B,80C 'lsa':8A,83C 'lsarpc':47B,98C 'machin':76B 'method':44B,95C 'microsoft':1A,3A,17A,78C 'ntlm':60B,68B,111C 'per':117C 'ransomwar':27B 'relay':66B 'requir':113C 'secur':6A,36B,81C 'server':58B,109C 'spoof':9A,30B,86C 'unauthent':40B,90C 'updat':116C 'use':110C 'vendor':118C 'vulner':10A,87C 'window':2A,4A,28B,34B,79C 'windows':18A","nicknames":[],"mitigations":[],"who_affected":null,"tier":null,"verified":{},"analyst_revisit_at":null,"first_public_at":"2021-08-12T18:15:10+00:00","kev":{"dateAdded":"2021-11-03","dueDate":"2021-11-17","requiredAction":"Apply updates per vendor instructions.","knownRansomwareCampaignUse":"Known"},"cvss_vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N","cvss_by":"secure@microsoft.com","poc_count":0,"sources":[{"source":"kev","external_id":"CVE-2021-36942","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-36942","severity":null,"published_at":"2021-11-03T00:00:00+00:00","modified_at":null,"first_seen_at":"2026-10-23T19:11:53+00:00","fetched_at":"2026-10-25T13:39:33+00:00","note":null},{"source":"epss","external_id":"CVE-2021-36942","url":"https://api.first.org/data/v1/epss?cve=CVE-2021-36942","severity":null,"published_at":null,"modified_at":null,"first_seen_at":"2026-10-23T19:13:43+00:00","fetched_at":"2026-10-23T19:13:43+00:00","note":null},{"source":"nvd","external_id":"CVE-2021-36942","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-36942","severity":null,"published_at":"2021-08-12T18:15:10+00:00","modified_at":"2026-08-10T20:19:03+00:00","first_seen_at":"2026-10-23T21:57:34+00:00","fetched_at":"2026-10-23T21:57:34+00:00","note":null}],"documents":[],"notice":"Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}