{"id":"CVE-2021-34484","kind":"vulnerability","aliases":["CVE-2021-34484"],"related":[],"title":"Microsoft Windows: Microsoft Windows User Profile Service Privilege Escalation Vulnerability","description":"Microsoft Windows User Profile Service contains an unspecified vulnerability that allows for privilege escalation.\n\nCISA required action: Apply updates per vendor instructions.","summary":"Microsoft Windows User Profile Service has a flaw that lets a local user raise their privileges. An attacker who already has a foothold on the machine can gain SYSTEM-level control.","severity":"high","cvss":7.8,"epss":0.21827,"exploited":true,"exploited_at":"2022-03-31T00:00:00+00:00","products":[{"name":"Microsoft Windows","fixed":[],"affected":"","ecosystem":"vendor"}],"ecosystems":["vendor"],"tags":["exploited","infrastructure","self-hosted","windows"],"not_affected_if":["patched-windows"],"how_to_check":"Check the installed Windows build against Microsoft's security update guide for CVE-2021-34484; the sources do not give a command.","fix":"Apply the Microsoft update for CVE-2021-34484 per vendor instructions, as CISA requires; the sources do not name the KB or build.","status":"open","published_at":"2021-08-12T18:15:09+00:00","first_seen_at":"2026-10-23T19:11:52+00:00","triaged_at":"2026-10-23T21:18:11+00:00","updated_at":"2026-10-23T21:57:35+00:00","category":"infrastructure","confidence":0.6,"triage":{"at":"2026-10-23T21:18:11Z","model":"claude-haiku-5-5","output":{"fix":"Apply the Microsoft update for CVE-2021-34484 per vendor instructions, as CISA requires; the sources do not name the KB or build.","reach":"local","impact":"high","summary":"Microsoft Windows User Profile Service has a flaw that lets a local user raise their privileges. An attacker who already has a foothold on the machine can gain SYSTEM-level control.","category":"infrastructure","who_cares":["windows","self-hosted"],"confidence":0.6,"needs_auth":"yes","worst_case":"local user gains SYSTEM privileges on the Windows machine","analyst_note":"Find the affected Windows builds and the KB number in Microsoft's security update guide for CVE-2021-34484; the sources only say 'unspecified'.","how_to_check":"Check the installed Windows build against Microsoft's security update guide for CVE-2021-34484; the sources do not give a command.\nunknown","needs_analyst":true,"not_affected_if":["patched-windows"],"user_interaction":"no","needs_special_setup":"no","severity_if_unknown":"high"},"cost_usd":0.00047,"input_tokens":2821,"output_tokens":375,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-2021':12A,15A '-34484':13A,16A 'action':73C 'allow':67C 'alreadi':44B 'appli':74C 'attack':42B 'cisa':71C 'contain':62C 'control':56B 'cve':11A,14A 'escal':9A,70C 'exploit':19B 'flaw':32B 'foothold':47B 'gain':52B 'host':23B 'infrastructur':20B 'instruct':78C 'let':34B 'level':55B 'local':36B 'machin':50B 'microsoft':1A,3A,17A,25B,57C 'per':76C 'privileg':8A,40B,69C 'profil':6A,28B,60C 'rais':38B 'requir':72C 'self':22B 'self-host':21B 'servic':7A,29B,61C 'system':54B 'system-level':53B 'unspecifi':64C 'updat':75C 'user':5A,27B,37B,59C 'vendor':77C 'vulner':10A,65C 'window':2A,4A,24B,26B,58C 'windows':18A","nicknames":[],"mitigations":[],"who_affected":null,"tier":null,"verified":{},"analyst_revisit_at":null,"first_public_at":"2021-08-12T18:15:09+00:00","kev":{"dateAdded":"2022-03-31","dueDate":"2022-04-21","requiredAction":"Apply updates per vendor instructions.","knownRansomwareCampaignUse":"Unknown"},"cvss_vector":"CVSS:3.1/AV:L/AC:L/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-2021-34484","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-34484","severity":null,"published_at":"2022-03-31T00:00:00+00:00","modified_at":null,"first_seen_at":"2026-10-23T19:11:52+00:00","fetched_at":"2026-10-25T14:39:40+00:00","note":null},{"source":"epss","external_id":"CVE-2021-34484","url":"https://api.first.org/data/v1/epss?cve=CVE-2021-34484","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-2021-34484","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-34484","severity":null,"published_at":"2021-08-12T18:15:09+00:00","modified_at":"2026-08-10T19:59:12+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"}