{"id":"CVE-2021-42278","kind":"vulnerability","aliases":["CVE-2021-42278"],"related":[],"title":"Microsoft Active Directory: Microsoft Active Directory Domain Services Privilege Escalation Vulnerability","description":"Microsoft Active Directory Domain Services contains an unspecified vulnerability that allows for privilege escalation.\n\nCISA required action: Apply updates per vendor instructions.","summary":"Microsoft Active Directory Domain Services has a privilege escalation flaw, the sAMAccountName spoofing issue tracked with CVE-2021-42278. CISA lists it as actively exploited, and an attacker with a low-privilege domain account can gain domain admin rights.","severity":"high","cvss":7.5,"epss":0.73297,"exploited":true,"exploited_at":"2022-04-11T00:00:00+00:00","products":[{"name":"Microsoft Active Directory","fixed":[],"affected":"","ecosystem":"vendor"}],"ecosystems":["vendor"],"tags":["active-directory","domain-controllers","exploited","infrastructure","ransomware","windows-server"],"not_affected_if":["no-active-directory"],"how_to_check":null,"fix":"Apply the Microsoft update for CVE-2021-42278 per vendor instructions (Microsoft guidance, not in the sources).","status":"open","published_at":"2021-11-10T01:19:44+00:00","first_seen_at":"2026-10-23T19:11:52+00:00","triaged_at":"2026-10-23T21:18:05+00:00","updated_at":"2026-10-23T21:57:35+00:00","category":"infrastructure","confidence":0.6,"triage":{"at":"2026-10-23T21:18:05Z","model":"claude-haiku-5-5","output":{"fix":"Apply the Microsoft update for CVE-2021-42278 per vendor instructions (Microsoft guidance, not in the sources).\nunknown","reach":"network","impact":"high","summary":"Microsoft Active Directory Domain Services has a privilege escalation flaw, the sAMAccountName spoofing issue tracked with CVE-2021-42278. CISA lists it as actively exploited, and an attacker with a low-privilege domain account can gain domain admin rights.","category":"infrastructure","who_cares":["active-directory","windows-server","domain-controllers"],"confidence":0.6,"needs_auth":"yes","worst_case":"Attacker with ordinary domain account becomes domain administrator.","analyst_note":"Confirm patch KB numbers and the sAMAccountName detection steps from Microsoft's CVE-2021-42278 advisory; sources give no version or check details.","how_to_check":"unknown","needs_analyst":true,"not_affected_if":["no-active-directory"],"user_interaction":"no","needs_special_setup":"no","severity_if_unknown":"high"},"cost_usd":0.000474,"input_tokens":2832,"output_tokens":381,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-2021':13A,16A,50B '-42278':14A,17A,51B 'account':67B 'action':89C 'activ':2A,5A,22B,34B,56B,74C 'active':19A 'active-directori':21B 'admin':71B 'allow':83C 'appli':90C 'attack':60B 'cisa':52B,87C 'contain':78C 'control':26B 'cve':12A,15A,49B 'directori':3A,6A,23B,35B,75C 'directory':20A 'domain':7A,25B,36B,66B,70B,76C 'domain-control':24B 'escal':10A,41B,86C 'exploit':27B,57B 'flaw':42B 'gain':69B 'infrastructur':28B 'instruct':94C 'issu':46B 'list':53B 'low':64B 'low-privileg':63B 'microsoft':1A,4A,18A,33B,73C 'per':92C 'privileg':9A,40B,65B,85C 'ransomwar':29B 'requir':88C 'right':72B 'samaccountnam':44B 'server':32B 'servic':8A,37B,77C 'spoof':45B 'track':47B 'unspecifi':80C 'updat':91C 'vendor':93C 'vulner':11A,81C 'window':31B 'windows-serv':30B","nicknames":[],"mitigations":[],"who_affected":null,"tier":null,"verified":{},"analyst_revisit_at":null,"first_public_at":"2021-11-10T01:19:44+00:00","kev":{"dateAdded":"2022-04-11","dueDate":"2022-05-02","requiredAction":"Apply updates per vendor instructions.","knownRansomwareCampaignUse":"Known"},"cvss_vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","cvss_by":"secure@microsoft.com","poc_count":0,"sources":[{"source":"kev","external_id":"CVE-2021-42278","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-42278","severity":null,"published_at":"2022-04-11T00:00:00+00:00","modified_at":null,"first_seen_at":"2026-10-23T19:11:52+00:00","fetched_at":"2026-10-25T11:39:16+00:00","note":null},{"source":"epss","external_id":"CVE-2021-42278","url":"https://api.first.org/data/v1/epss?cve=CVE-2021-42278","severity":null,"published_at":null,"modified_at":null,"first_seen_at":"2026-10-23T19:13:44+00:00","fetched_at":"2026-10-23T19:13:44+00:00","note":null},{"source":"nvd","external_id":"CVE-2021-42278","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-42278","severity":null,"published_at":"2021-11-10T01:19:44+00:00","modified_at":"2026-08-19T19:22:57+00:00","first_seen_at":"2026-10-23T21:57:35+00:00","fetched_at":"2026-10-23T21:57:35+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"}