{"id":"CVE-2021-41379","kind":"vulnerability","aliases":["CVE-2021-41379"],"related":[],"title":"Microsoft Windows: Microsoft Windows Installer Privilege Escalation Vulnerability","description":"Microsoft Windows Installer contains an unspecified vulnerability that allows for privilege escalation.\n\nCISA required action: Apply updates per vendor instructions.","summary":"Microsoft Windows Installer has a flaw that lets a low-privileged local user escalate to higher privileges on the machine. CISA lists it as known exploited, and the sources note ransomware use.","severity":"high","cvss":7.8,"epss":0.19452,"exploited":true,"exploited_at":"2022-03-03T00:00:00+00:00","products":[{"name":"Microsoft Windows","fixed":[],"affected":"","ecosystem":"vendor"}],"ecosystems":["vendor"],"tags":["exploited","infrastructure","multi-user-machines","ransomware","windows","windows-servers"],"not_affected_if":["unknown"],"how_to_check":null,"fix":"Apply the Microsoft security update for CVE-2021-41379 per vendor instructions (CISA KEV required action).","status":"open","published_at":"2021-11-10T01:19:32+00:00","first_seen_at":"2026-10-23T19:11:52+00:00","triaged_at":"2026-10-23T21:24:27+00:00","updated_at":"2026-10-23T21:57:35+00:00","category":"infrastructure","confidence":0.6,"triage":{"at":"2026-10-23T21:24:27Z","model":"claude-haiku-5-5","output":{"fix":"Apply the Microsoft security update for CVE-2021-41379 per vendor instructions (CISA KEV required action).\nunknown","reach":"local","impact":"high","summary":"Microsoft Windows Installer has a flaw that lets a low-privileged local user escalate to higher privileges on the machine. CISA lists it as known exploited, and the sources note ransomware use.","category":"infrastructure","who_cares":["windows","windows-servers","multi-user-machines"],"confidence":0.6,"needs_auth":"yes","worst_case":"local user gains SYSTEM privileges on the Windows machine","analyst_note":"Find the Microsoft Security Response Center advisory for CVE-2021-41379 to confirm affected Windows builds, the patch KB numbers, and any detection steps.","how_to_check":"unknown","needs_analyst":true,"not_affected_if":["unknown"],"user_interaction":"unknown","needs_special_setup":"unknown","severity_if_unknown":"high"},"cost_usd":0.000456,"input_tokens":2820,"output_tokens":349,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-2021':10A,13A '-41379':11A,14A 'action':75C 'allow':69C 'appli':76C 'cisa':49B,73C 'contain':64C 'cve':9A,12A 'escal':7A,42B,72C 'exploit':17B,54B 'flaw':33B 'higher':44B 'infrastructur':18B 'instal':5A,30B,63C 'instruct':80C 'known':53B 'let':35B 'list':50B 'local':40B 'low':38B 'low-privileg':37B 'machin':22B,48B 'microsoft':1A,3A,15A,28B,61C 'multi':20B 'multi-user-machin':19B 'note':58B 'per':78C 'privileg':6A,39B,45B,71C 'ransomwar':23B,59B 'requir':74C 'server':27B 'sourc':57B 'unspecifi':66C 'updat':77C 'use':60B 'user':21B,41B 'vendor':79C 'vulner':8A,67C 'window':2A,4A,24B,26B,29B,62C 'windows':16A 'windows-serv':25B","nicknames":[],"mitigations":[],"who_affected":null,"tier":null,"verified":{},"analyst_revisit_at":null,"first_public_at":"2021-11-10T01:19:32+00:00","kev":{"dateAdded":"2022-03-03","dueDate":"2022-03-17","requiredAction":"Apply updates per vendor instructions.","knownRansomwareCampaignUse":"Known"},"cvss_vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","cvss_by":"secure@microsoft.com","poc_count":0,"sources":[{"source":"kev","external_id":"CVE-2021-41379","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-41379","severity":null,"published_at":"2022-03-03T00:00:00+00:00","modified_at":null,"first_seen_at":"2026-10-23T19:11:52+00:00","fetched_at":"2026-10-25T11:39:17+00:00","note":null},{"source":"epss","external_id":"CVE-2021-41379","url":"https://api.first.org/data/v1/epss?cve=CVE-2021-41379","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-2021-41379","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-41379","severity":null,"published_at":"2021-11-10T01:19:32+00:00","modified_at":"2026-08-19T19:22:46+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"}