{"id":"CVE-2026-123377","kind":"vulnerability","aliases":["CVE-2026-123377"],"related":[],"title":"Microsoft Outlook: heap buffer overflow lets a network attacker run code","description":"Heap-based buffer overflow in Microsoft Office Outlook allows an unauthorized attacker to execute code over a network.","summary":"A heap-based buffer overflow in Microsoft Office Outlook lets an unauthorized attacker run code over a network. Successful exploitation would give the attacker code execution on the affected machine.","severity":"high","cvss":8.8,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["microsoft-office","outlook","package","windows"],"not_affected_if":[],"how_to_check":null,"fix":null,"status":"open","published_at":"2026-11-10T19:20:40+00:00","first_seen_at":"2026-11-10T19:25:12+00:00","triaged_at":"2026-11-10T19:27:40+00:00","updated_at":"2026-11-10T19:27:40+00:00","category":"package","confidence":0.5,"triage":{"at":"2026-11-10T19:27:40Z","model":"claude-haiku-5-5","output":{"fix":"unknown","reach":"network","title":"Microsoft Outlook: heap buffer overflow lets a network attacker run code","impact":"high","summary":"A heap-based buffer overflow in Microsoft Office Outlook lets an unauthorized attacker run code over a network. Successful exploitation would give the attacker code execution on the affected machine.","audience":"everyone","category":"package","nicknames":[],"who_cares":["outlook","microsoft-office","windows"],"confidence":0.5,"fix_status":"unknown","needs_auth":"no","worst_case":"Attacker runs code on the Outlook user's machine over the network.","analyst_note":"Check the Microsoft Security Update Guide entry for CVE-2026-123377 for affected versions, fixed builds and whether user interaction (such as opening a message) is required.","how_to_check":"- unknown","plain_action":"Update Microsoft Outlook to the latest version through Microsoft's update channel once Microsoft releases a fix.","product_name":"","needs_analyst":true,"not_affected_if":[],"who_is_affected":"Microsoft Office Outlook installations are affected according to the NVD entry. The sources do not name affected versions, editions or configurations, so the exact exposure is unknown.","user_interaction":"unknown","product_ecosystem":"","needs_special_setup":"unknown","severity_if_unknown":"high"},"cost_usd":0.000682,"input_tokens":4498,"output_tokens":464,"severity_before":"high"},"analyst_status":"queued","analyst_note":"Check the Microsoft Security Update Guide entry for CVE-2026-123377 for affected versions, fixed builds and whether user interaction (such as opening a message) is required.","search":"'-123377':14A,17A '-2026':13A,16A 'affect':53B 'allow':64C 'attack':9A,37B,48B,67C 'base':27B,57C 'buffer':4A,28B,58C 'code':11A,39B,49B,70C 'cve':12A,15A 'execut':50B,69C 'exploit':44B 'give':46B 'heap':3A,26B,56C 'heap-bas':25B,55C 'let':6A,34B 'machin':54B 'microsoft':1A,19B,31B,61C 'microsoft-offic':18B 'network':8A,42B,73C 'offic':20B,32B,62C 'outlook':2A,21B,33B,63C 'overflow':5A,29B,59C 'packag':22B 'run':10A,38B 'success':43B 'unauthor':36B,66C 'window':23B 'would':45B","nicknames":[],"mitigations":[],"who_affected":"Microsoft Office Outlook installations are affected according to the NVD entry. The sources do not name affected versions, editions or configurations, so the exact exposure is unknown.","tier":"B","verified":{},"analyst_revisit_at":null,"fix_status":"none","audience":"everyone","plain_action":"Update Microsoft Outlook to the latest version through Microsoft's update channel once Microsoft releases a fix.","pkeys":[],"ptokens":[],"labels":["high","microsoftoffice","outlook","package","windows"],"campaign_type":null,"search_a":"'-123377':14A,17A '-2026':13A,16A 'attack':9A 'buffer':4A 'code':11A 'cve':12A,15A 'heap':3A 'let':6A 'microsoft':1A 'network':8A 'outlook':2A 'overflow':5A 'run':10A","search_b":"'affect':53B 'attack':37B,48B 'base':27B 'buffer':28B 'code':39B,49B 'execut':50B 'exploit':44B 'give':46B 'heap':26B 'heap-bas':25B 'let':34B 'machin':54B 'microsoft':19B,31B 'microsoft-offic':18B 'network':42B 'offic':20B,32B 'outlook':21B,33B 'overflow':29B 'packag':22B 'run':38B 'success':43B 'unauthor':36B 'window':23B 'would':45B","search_c":"'allow':64C 'attack':67C 'base':57C 'buffer':58C 'code':70C 'execut':69C 'heap':56C 'heap-bas':55C 'microsoft':61C 'network':73C 'offic':62C 'outlook':63C 'overflow':59C 'unauthor':66C","cause_entry":null,"cause_path":null,"disclosures_checked_at":null,"first_public_at":"2026-11-10T19:20:40+00:00","kev":null,"cvss_vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","cvss_by":"secure@microsoft.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-123377","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-123377","severity":null,"published_at":"2026-11-10T19:20:40+00:00","modified_at":"2026-11-10T19:20:41+00:00","first_seen_at":"2026-11-10T19:25:12+00:00","fetched_at":"2026-11-10T19:25:12+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"}