{"id":"CVE-2021-31955","kind":"vulnerability","aliases":["CVE-2021-31955"],"related":[],"title":"Microsoft Windows: Microsoft Windows Kernel Information Disclosure Vulnerability","description":"Microsoft Windows Kernel contains an unspecified vulnerability that allows for information disclosure. Successful exploitation allows attackers to read the contents of kernel memory from a user-mode process.\n\nCISA required action: Apply updates per vendor instructions.","summary":"A flaw in the Windows kernel lets a process read kernel memory it should not see. It is listed in CISA's known-exploited catalog, so attackers are using it in real attacks.","severity":"medium","cvss":5.5,"epss":0.81107,"exploited":true,"exploited_at":"2021-11-03T00:00:00+00:00","products":[{"name":"Microsoft Windows","fixed":[],"affected":"","ecosystem":"vendor"}],"ecosystems":["vendor"],"tags":["exploited","infrastructure","windows"],"not_affected_if":["patched-windows"],"how_to_check":null,"fix":"Apply the Microsoft Windows update that addresses CVE-2021-31955, per vendor instructions. Exact patch names are not in the sources.","status":"open","published_at":"2021-06-08T23:15:08+00:00","first_seen_at":"2026-10-23T19:11:53+00:00","triaged_at":"2026-10-23T21:37:33+00:00","updated_at":"2026-10-23T21:57:35+00:00","category":"infrastructure","confidence":0.6,"triage":{"at":"2026-10-23T21:37:33Z","model":"claude-haiku-5-5","output":{"fix":"Apply the Microsoft Windows update that addresses CVE-2021-31955, per vendor instructions. Exact patch names are not in the sources.","reach":"local","impact":"medium","summary":"A flaw in the Windows kernel lets a process read kernel memory it should not see. It is listed in CISA's known-exploited catalog, so attackers are using it in real attacks.","category":"infrastructure","who_cares":["windows"],"confidence":0.6,"needs_auth":"yes","worst_case":"Local process reads kernel memory, aiding privilege escalation chains","analyst_note":"Find the Microsoft advisory for CVE-2021-31955 to get affected builds, patch KB numbers and a check method; the sources give none.","how_to_check":"unknown","needs_analyst":true,"not_affected_if":["patched-windows"],"user_interaction":"no","needs_special_setup":"unknown","severity_if_unknown":"low"},"cost_usd":0.000448,"input_tokens":2846,"output_tokens":327,"severity_before":"unknown"},"analyst_status":"queued","analyst_note":"Find the Microsoft advisory for CVE-2021-31955 to get affected builds, patch KB numbers and a check method; the sources give none.","search":"'-2021':10A,13A '-31955':11A,14A 'action':85C 'allow':62C,68C 'appli':86C 'attack':47B,53B,69C 'catalog':45B 'cisa':40B,83C 'contain':57C 'content':73C 'cve':9A,12A 'disclosur':7A,65C 'exploit':17B,44B,67C 'flaw':21B 'inform':6A,64C 'infrastructur':18B 'instruct':90C 'kernel':5A,25B,30B,56C,75C 'known':43B 'known-exploit':42B 'let':26B 'list':38B 'memori':31B,76C 'microsoft':1A,3A,15A,54C 'mode':81C 'per':88C 'process':28B,82C 'read':29B,71C 'real':52B 'requir':84C 'see':35B 'success':66C 'unspecifi':59C 'updat':87C 'use':49B 'user':80C 'user-mod':79C 'vendor':89C 'vulner':8A,60C 'window':2A,4A,19B,24B,55C 'windows':16A","nicknames":[],"mitigations":[],"who_affected":null,"tier":null,"verified":{},"analyst_revisit_at":null,"first_public_at":"2021-06-08T23:15:08+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:N/A:N","cvss_by":"secure@microsoft.com","poc_count":0,"sources":[{"source":"kev","external_id":"CVE-2021-31955","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-31955","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":"2026-10-25T16:39:50+00:00","note":null},{"source":"epss","external_id":"CVE-2021-31955","url":"https://api.first.org/data/v1/epss?cve=CVE-2021-31955","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-2021-31955","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-31955","severity":null,"published_at":"2021-06-08T23:15:08+00:00","modified_at":"2026-06-17T03:52:33+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"}