{"id":"CVE-2021-33742","kind":"vulnerability","aliases":["CVE-2021-33742"],"related":[],"title":"Microsoft Windows: Microsoft Windows MSHTML Platform Remote Code Execution Vulnerability","description":"Microsoft Windows MSHTML Platform contains an unspecified vulnerability that allows for remote code execution.\n\nCISA required action: Apply updates per vendor instructions.","summary":"Microsoft Windows MSHTML Platform, the browser engine component used by Windows, has a remote code execution flaw. Attackers are exploiting it in the wild, so a crafted file or page can run code on the affected machine.","severity":"high","cvss":8.8,"epss":0.59407,"exploited":true,"exploited_at":"2021-11-03T00:00:00+00:00","products":[{"name":"Microsoft Windows","fixed":[],"affected":"","ecosystem":"vendor"}],"ecosystems":["vendor"],"tags":["desktop","exploited","infrastructure","office","windows"],"not_affected_if":["patched-windows"],"how_to_check":null,"fix":"Apply the Microsoft security update for CVE-2021-33742 per vendor instructions, as CISA requires.","status":"open","published_at":"2021-06-08T23:15:09+00:00","first_seen_at":"2026-10-23T19:11:53+00:00","triaged_at":"2026-10-23T21:39:30+00:00","updated_at":"2026-10-23T21:57:35+00:00","category":"infrastructure","confidence":0.6,"triage":{"at":"2026-10-23T21:39:30Z","model":"claude-haiku-5-5","output":{"fix":"Apply the Microsoft security update for CVE-2021-33742 per vendor instructions, as CISA requires.\nunknown","reach":"internet","impact":"high","summary":"Microsoft Windows MSHTML Platform, the browser engine component used by Windows, has a remote code execution flaw. Attackers are exploiting it in the wild, so a crafted file or page can run code on the affected machine.","category":"infrastructure","who_cares":["windows","desktop","office"],"confidence":0.6,"needs_auth":"no","worst_case":"Attacker runs code on the Windows machine after a user opens crafted content","analyst_note":"Find the patched Windows builds and the exploit delivery vector (Office document or web content) in Microsoft's CVE-2021-33742 advisory, linked from the CISA KEV entry.","how_to_check":"unknown","needs_analyst":true,"not_affected_if":["patched-windows"],"user_interaction":"yes","needs_special_setup":"unknown","severity_if_unknown":"high"},"cost_usd":0.000461,"input_tokens":2824,"output_tokens":358,"severity_before":"unknown"},"analyst_status":"queued","analyst_note":"Find the patched Windows builds and the exploit delivery vector (Office document or web content) in Microsoft's CVE-2021-33742 advisory, linked from the CISA KEV entry.","search":"'-2021':12A,15A '-33742':13A,16A 'action':77C 'affect':59B 'allow':70C 'appli':78C 'attack':41B 'browser':29B 'cisa':75C 'code':8A,38B,56B,73C 'compon':31B 'contain':65C 'craft':50B 'cve':11A,14A 'desktop':19B 'engin':30B 'execut':9A,39B,74C 'exploit':20B,43B 'file':51B 'flaw':40B 'infrastructur':21B 'instruct':82C 'machin':60B 'microsoft':1A,3A,17A,24B,61C 'mshtml':5A,26B,63C 'offic':22B 'page':53B 'per':80C 'platform':6A,27B,64C 'remot':7A,37B,72C 'requir':76C 'run':55B 'unspecifi':67C 'updat':79C 'use':32B 'vendor':81C 'vulner':10A,68C 'wild':47B 'window':2A,4A,23B,25B,34B,62C 'windows':18A","nicknames":[],"mitigations":[],"who_affected":null,"tier":null,"verified":{},"analyst_revisit_at":null,"first_public_at":"2021-06-08T23:15:09+00:00","kev":{"dateAdded":"2021-11-03","dueDate":"2021-11-17","requiredAction":"Apply updates per vendor instructions.","knownRansomwareCampaignUse":"Unknown"},"cvss_vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H","cvss_by":"secure@microsoft.com","poc_count":0,"sources":[{"source":"kev","external_id":"CVE-2021-33742","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-33742","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":"2026-10-25T12:39:25+00:00","note":null},{"source":"epss","external_id":"CVE-2021-33742","url":"https://api.first.org/data/v1/epss?cve=CVE-2021-33742","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-2021-33742","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-33742","severity":null,"published_at":"2021-06-08T23:15:09+00:00","modified_at":"2026-06-17T03:55:08+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"}