{"id":"CVE-2021-28310","kind":"vulnerability","aliases":["CVE-2021-28310"],"related":[],"title":"Microsoft Win32k: Microsoft Win32k Privilege Escalation Vulnerability","description":"Microsoft Windows Win32k contains an unspecified vulnerability that allows for privilege escalation.\n\nCISA required action: Apply updates per vendor instructions.","summary":"Win32k is the Windows kernel-mode graphics driver, and this flaw lets a process that is already running on the machine raise its privileges. An attacker with a foothold, such as a low-privilege user account or malware, can gain SYSTEM-level control of the Windows host.","severity":"high","cvss":7.8,"epss":0.08398,"exploited":true,"exploited_at":"2021-11-03T00:00:00+00:00","products":[{"name":"Microsoft Win32k","fixed":[],"affected":"","ecosystem":"vendor"}],"ecosystems":["vendor"],"tags":["desktop","exploited","infrastructure","self-hosted","windows"],"not_affected_if":["fully-patched-windows","non-windows"],"how_to_check":"Check the installed Windows build against Microsoft's April 2021 security update for CVE-2021-28310 (run winver or Get-HotFix and compare to the advisory).","fix":"Install Microsoft's April 2021 security update for CVE-2021-28310 on every affected Windows host, then reboot.","status":"open","published_at":"2021-04-13T20:15:16+00:00","first_seen_at":"2026-10-23T19:11:53+00:00","triaged_at":"2026-10-23T21:39:19+00:00","updated_at":"2026-10-23T21:57:34+00:00","category":"infrastructure","confidence":0.6,"triage":{"at":"2026-10-23T21:39:19Z","model":"claude-haiku-5-5","output":{"fix":"Install Microsoft's April 2021 security update for CVE-2021-28310 on every affected Windows host, then reboot.\nunknown","reach":"local","impact":"high","summary":"Win32k is the Windows kernel-mode graphics driver, and this flaw lets a process that is already running on the machine raise its privileges. An attacker with a foothold, such as a low-privilege user account or malware, can gain SYSTEM-level control of the Windows host.","category":"infrastructure","who_cares":["windows","self-hosted","desktop"],"confidence":0.6,"needs_auth":"yes","worst_case":"Local attacker gains SYSTEM privileges on the Windows machine.","analyst_note":"Confirm the exact fixed Windows builds and KB numbers from Microsoft's CVE-2021-28310 advisory; the sources here give no version details.","how_to_check":"Check the installed Windows build against Microsoft's April 2021 security update for CVE-2021-28310 (run winver or Get-HotFix and compare to the advisory).\nunknown\nunknown","needs_analyst":true,"not_affected_if":["fully-patched-windows","non-windows"],"user_interaction":"no","needs_special_setup":"no","severity_if_unknown":"high"},"cost_usd":0.0005,"input_tokens":2816,"output_tokens":437,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-2021':9A,12A '-28310':10A,13A 'account':60B 'action':87C 'allow':81C 'alreadi':40B 'appli':88C 'attack':49B 'cisa':85C 'contain':76C 'control':68B 'cve':8A,11A 'desktop':16B 'driver':31B 'escal':6A,84C 'exploit':17B 'flaw':34B 'foothold':52B 'gain':64B 'graphic':30B 'host':21B,72B 'infrastructur':18B 'instruct':92C 'kernel':28B 'kernel-mod':27B 'let':35B 'level':67B 'low':57B 'low-privileg':56B 'machin':44B 'malwar':62B 'microsoft':1A,3A,14A,73C 'mode':29B 'per':90C 'privileg':5A,47B,58B,83C 'process':37B 'rais':45B 'requir':86C 'run':41B 'self':20B 'self-host':19B 'system':66B 'system-level':65B 'unspecifi':78C 'updat':89C 'user':59B 'vendor':91C 'vulner':7A,79C 'win32k':2A,4A,15A,23B,75C 'window':22B,26B,71B,74C","nicknames":[],"mitigations":[],"who_affected":null,"tier":null,"verified":{},"analyst_revisit_at":null,"first_public_at":"2021-04-13T20:15:16+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: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-2021-28310","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-28310","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":"2026-10-25T14:39:41+00:00","note":null},{"source":"epss","external_id":"CVE-2021-28310","url":"https://api.first.org/data/v1/epss?cve=CVE-2021-28310","severity":null,"published_at":null,"modified_at":null,"first_seen_at":"2026-10-23T19:13:43+00:00","fetched_at":"2026-10-23T19:13:43+00:00","note":null},{"source":"nvd","external_id":"CVE-2021-28310","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-28310","severity":null,"published_at":"2021-04-13T20:15:16+00:00","modified_at":"2026-06-17T03:46:08+00:00","first_seen_at":"2026-10-23T21:57:34+00:00","fetched_at":"2026-10-23T21:57:34+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"}