{"id":"CVE-2026-119921","kind":"vulnerability","aliases":["CVE-2026-119921"],"related":[],"title":"Windows: Microsoft Account Sign-in Assistant heap overflow grants local privilege escalation","description":"Heap-based buffer overflow in Windows Microsoft Account Sign-in Assistant allows an authorized attacker to elevate privileges locally.","summary":"A heap-based buffer overflow in the Windows Microsoft Account Sign-in Assistant service lets a signed-in attacker raise their privileges on the same machine. The sources give a CVSS score of 7.0 and no details of the affected Windows versions or fix.","severity":"high","cvss":7.0,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["infrastructure","microsoft-account","windows"],"not_affected_if":["no-local-user-access"],"how_to_check":null,"fix":null,"status":"open","published_at":"2026-11-10T19:20:14+00:00","first_seen_at":"2026-11-10T19:25:03+00:00","triaged_at":"2026-11-10T19:51:27+00:00","updated_at":"2026-11-10T19:51:27+00:00","category":"infrastructure","confidence":0.6,"triage":{"at":"2026-11-10T19:51:27Z","model":"claude-haiku-5-5","output":{"fix":"unknown","reach":"local","title":"Windows: Microsoft Account Sign-in Assistant heap overflow grants local privilege escalation","impact":"high","summary":"A heap-based buffer overflow in the Windows Microsoft Account Sign-in Assistant service lets a signed-in attacker raise their privileges on the same machine. The sources give a CVSS score of 7.0 and no details of the affected Windows versions or fix.","audience":"businesses","category":"infrastructure","nicknames":[],"who_cares":["windows","microsoft-account"],"confidence":0.6,"fix_status":"unknown","needs_auth":"yes","worst_case":"local user gains SYSTEM-level privileges on the machine","analyst_note":"Find the Microsoft Security Response Center advisory for CVE-2026-119921 to get affected Windows builds and the patch.","how_to_check":"unknown","plain_action":"","product_name":"","needs_analyst":true,"not_affected_if":["no-local-user-access"],"who_is_affected":"Windows machines with the Microsoft Account Sign-in Assistant service present. The sources do not list affected Windows builds or whether the service is disabled by default. An attacker needs an existing local account on the machine.","user_interaction":"no","product_ecosystem":"","needs_special_setup":"unknown","severity_if_unknown":"high"},"cost_usd":0.00068,"input_tokens":4510,"output_tokens":458,"severity_before":"high"},"analyst_status":"queued","analyst_note":"Find the Microsoft Security Response Center advisory for CVE-2026-119921 to get affected Windows builds and the patch.","search":"'-119921':16A,19A '-2026':15A,18A '7.0':61B 'account':3A,23B,35B,80C 'affect':67B 'allow':85C 'assist':7A,39B,84C 'attack':46B,88C 'author':87C 'base':28B,74C 'buffer':29B,75C 'cve':14A,17A 'cvss':58B 'detail':64B 'elev':90C 'escal':13A 'fix':71B 'give':56B 'grant':10A 'heap':8A,27B,73C 'heap-bas':26B,72C 'infrastructur':20B 'let':41B 'local':11A,92C 'machin':53B 'microsoft':2A,22B,34B,79C 'microsoft-account':21B 'overflow':9A,30B,76C 'privileg':12A,49B,91C 'rais':47B 'score':59B 'servic':40B 'sign':5A,37B,44B,82C 'sign-in':4A,36B,81C 'signed-in':43B 'sourc':55B 'version':69B 'window':1A,24B,33B,68B,78C","nicknames":[],"mitigations":[],"who_affected":"Windows machines with the Microsoft Account Sign-in Assistant service present. The sources do not list affected Windows builds or whether the service is disabled by default. An attacker needs an existing local account on the machine.","tier":"B","verified":{},"analyst_revisit_at":null,"fix_status":"none","audience":"businesses","plain_action":null,"pkeys":[],"ptokens":[],"labels":["high","infrastructure","microsoftaccount","windows"],"campaign_type":null,"search_a":"'-119921':16A,19A '-2026':15A,18A 'account':3A 'assist':7A 'cve':14A,17A 'escal':13A 'grant':10A 'heap':8A 'local':11A 'microsoft':2A 'overflow':9A 'privileg':12A 'sign':5A 'sign-in':4A 'window':1A","search_b":"'7.0':61B 'account':23B,35B 'affect':67B 'assist':39B 'attack':46B 'base':28B 'buffer':29B 'cvss':58B 'detail':64B 'fix':71B 'give':56B 'heap':27B 'heap-bas':26B 'infrastructur':20B 'let':41B 'machin':53B 'microsoft':22B,34B 'microsoft-account':21B 'overflow':30B 'privileg':49B 'rais':47B 'score':59B 'servic':40B 'sign':37B,44B 'sign-in':36B 'signed-in':43B 'sourc':55B 'version':69B 'window':24B,33B,68B","search_c":"'account':80C 'allow':85C 'assist':84C 'attack':88C 'author':87C 'base':74C 'buffer':75C 'elev':90C 'heap':73C 'heap-bas':72C 'local':92C 'microsoft':79C 'overflow':76C 'privileg':91C 'sign':82C 'sign-in':81C 'window':78C","cause_entry":null,"cause_path":null,"disclosures_checked_at":null,"first_public_at":"2026-11-10T19:20:14+00:00","kev":null,"cvss_vector":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","cvss_by":"secure@microsoft.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-119921","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-119921","severity":null,"published_at":"2026-11-10T19:20:14+00:00","modified_at":"2026-11-10T19:20:14+00:00","first_seen_at":"2026-11-10T19:25:03+00:00","fetched_at":"2026-11-10T19:25:03+00:00","note":null}],"documents":[],"disclosures":[],"exploit_sources":[],"notice":"Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai"}