{"id":"CVE-2021-40449","kind":"vulnerability","aliases":["CVE-2021-40449"],"related":[],"title":"Microsoft Windows: Microsoft Windows Win32k Privilege Escalation Vulnerability","description":"Unspecified vulnerability allows for an authenticated user to escalate privileges.\n\nCISA required action: Apply updates per vendor instructions.","summary":"A flaw in the Windows Win32k kernel driver lets a logged-in user raise their privileges on the machine. CISA lists it as actively exploited, and ransomware campaigns have used it.","severity":"high","cvss":7.8,"epss":0.81936,"exploited":true,"exploited_at":"2021-11-17T00:00:00+00:00","products":[{"name":"Microsoft Windows","fixed":[],"affected":"","ecosystem":"vendor"}],"ecosystems":["vendor"],"tags":["exploited","infrastructure","ransomware","self-hosted","windows"],"not_affected_if":["patched-windows"],"how_to_check":null,"fix":"Apply the Microsoft security update for CVE-2021-40449 per vendor instructions (CISA KEV required action).","status":"open","published_at":"2021-10-13T01:15:09+00:00","first_seen_at":"2026-10-23T19:11:53+00:00","triaged_at":"2026-10-23T21:32:00+00:00","updated_at":"2026-10-23T21:57:35+00:00","category":"infrastructure","confidence":0.6,"triage":{"at":"2026-10-23T21:32:00Z","model":"claude-haiku-5-5","output":{"fix":"Apply the Microsoft security update for CVE-2021-40449 per vendor instructions (CISA KEV required action).\nunknown","reach":"local","impact":"high","summary":"A flaw in the Windows Win32k kernel driver lets a logged-in user raise their privileges on the machine. CISA lists it as actively exploited, and ransomware campaigns have used it.","category":"infrastructure","who_cares":["windows","self-hosted"],"confidence":0.6,"needs_auth":"yes","worst_case":"Local user gains SYSTEM-level control of the Windows machine.","analyst_note":"Find the Microsoft Security Response Center advisory for CVE-2021-40449 to confirm affected Windows builds and the patch KB numbers; the sources here give no version or check command.","how_to_check":"unknown","needs_analyst":true,"not_affected_if":["patched-windows"],"user_interaction":"no","needs_special_setup":"no","severity_if_unknown":"high"},"cost_usd":0.000453,"input_tokens":2814,"output_tokens":344,"severity_before":"unknown"},"analyst_status":"queued","analyst_note":"Find the Microsoft Security Response Center advisory for CVE-2021-40449 to confirm affected Windows builds and the patch KB numbers; the sources here give no version or check command.","search":"'-2021':10A,13A '-40449':11A,14A 'action':67C 'activ':48B 'allow':57C 'appli':68C 'authent':60C 'campaign':52B 'cisa':44B,65C 'cve':9A,12A 'driver':31B 'escal':7A,63C 'exploit':17B,49B 'flaw':25B 'host':22B 'infrastructur':18B 'instruct':72C 'kernel':30B 'let':32B 'list':45B 'log':35B 'logged-in':34B 'machin':43B 'microsoft':1A,3A,15A 'per':70C 'privileg':6A,40B,64C 'rais':38B 'ransomwar':19B,51B 'requir':66C 'self':21B 'self-host':20B 'unspecifi':55C 'updat':69C 'use':54B 'user':37B,61C 'vendor':71C 'vulner':8A,56C 'win32k':5A,29B 'window':2A,4A,23B,28B 'windows':16A","nicknames":[],"mitigations":[],"who_affected":null,"tier":null,"verified":{},"analyst_revisit_at":null,"first_public_at":"2021-10-13T01:15:09+00:00","kev":{"dateAdded":"2021-11-17","dueDate":"2021-12-01","requiredAction":"Apply updates per vendor instructions.","knownRansomwareCampaignUse":"Known"},"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-2021-40449","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-40449","severity":null,"published_at":"2021-11-17T00:00:00+00:00","modified_at":null,"first_seen_at":"2026-10-23T19:11:53+00:00","fetched_at":"2026-10-25T17:39:58+00:00","note":null},{"source":"epss","external_id":"CVE-2021-40449","url":"https://api.first.org/data/v1/epss?cve=CVE-2021-40449","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-2021-40449","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-40449","severity":null,"published_at":"2021-10-13T01:15:09+00:00","modified_at":"2026-06-17T04:06:56+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"}