{"id":"CVE-2026-123380","kind":"vulnerability","aliases":["CVE-2026-123380"],"related":[],"title":"Microsoft Outlook: heap overflow lets an attacker run code over network","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 execute code over a network. The sources rate it high (CVSS 8.8) and do not describe the trigger or any user action needed.","severity":"high","cvss":8.8,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["microsoft-office","other","outlook","windows"],"not_affected_if":[],"how_to_check":"- Check the installed Outlook build in File > Account > About Outlook, or the Office build in `Microsoft Office Outlook` version details.","fix":null,"status":"open","published_at":"2026-11-10T19:20:41+00:00","first_seen_at":"2026-11-10T19:25:12+00:00","triaged_at":"2026-11-10T19:27:39+00:00","updated_at":"2026-11-10T19:27:39+00:00","category":"other","confidence":0.5,"triage":{"at":"2026-11-10T19:27:39Z","model":"claude-haiku-5-5","output":{"fix":"unknown","reach":"network","title":"Microsoft Outlook: heap overflow lets an attacker run code over network","impact":"high","summary":"A heap-based buffer overflow in Microsoft Office Outlook lets an unauthorized attacker execute code over a network. The sources rate it high (CVSS 8.8) and do not describe the trigger or any user action needed.","audience":"businesses","category":"other","nicknames":[],"who_cares":["outlook","microsoft-office","windows"],"confidence":0.5,"fix_status":"unknown","needs_auth":"unknown","worst_case":"Attacker runs code on the affected machine over the network","analyst_note":"Find the Microsoft Security Response Center advisory for CVE-2026-123380 to get affected builds, the trigger, and the patch.","how_to_check":"- Check the installed Outlook build in File > Account > About Outlook, or the Office build in `Microsoft Office Outlook` version details.\n- unknown","plain_action":"","product_name":"","needs_analyst":true,"not_affected_if":[],"who_is_affected":"Organizations running Microsoft Office Outlook; the sources do not list affected builds or the trigger path. unknown","user_interaction":"unknown","product_ecosystem":"","needs_special_setup":"unknown","severity_if_unknown":"high"},"cost_usd":0.000674,"input_tokens":4498,"output_tokens":449,"severity_before":"high"},"analyst_status":"queued","analyst_note":"Find the Microsoft Security Response Center advisory for CVE-2026-123380 to get affected builds, the trigger, and the patch.","search":"'-123380':14A,17A '-2026':13A,16A '8.8':49B 'action':59B 'allow':70C 'attack':7A,37B,73C 'base':27B,63C 'buffer':28B,64C 'code':9A,39B,76C 'cve':12A,15A 'cvss':48B 'describ':53B 'execut':38B,75C 'heap':3A,26B,62C 'heap-bas':25B,61C 'high':47B 'let':5A,34B 'microsoft':1A,19B,31B,67C 'microsoft-offic':18B 'need':60B 'network':11A,42B,79C 'offic':20B,32B,68C 'outlook':2A,22B,33B,69C 'overflow':4A,29B,65C 'rate':45B 'run':8A 'sourc':44B 'trigger':55B 'unauthor':36B,72C 'user':58B 'window':23B","nicknames":[],"mitigations":[],"who_affected":"Organizations running Microsoft Office Outlook; the sources do not list affected builds or the trigger path. unknown","tier":"B","verified":{},"analyst_revisit_at":null,"fix_status":"none","audience":"businesses","plain_action":null,"pkeys":[],"ptokens":[],"labels":["high","microsoftoffice","other","outlook","windows"],"campaign_type":null,"search_a":"'-123380':14A,17A '-2026':13A,16A 'attack':7A 'code':9A 'cve':12A,15A 'heap':3A 'let':5A 'microsoft':1A 'network':11A 'outlook':2A 'overflow':4A 'run':8A","search_b":"'8.8':49B 'action':59B 'attack':37B 'base':27B 'buffer':28B 'code':39B 'cvss':48B 'describ':53B 'execut':38B 'heap':26B 'heap-bas':25B 'high':47B 'let':34B 'microsoft':19B,31B 'microsoft-offic':18B 'need':60B 'network':42B 'offic':20B,32B 'outlook':22B,33B 'overflow':29B 'rate':45B 'sourc':44B 'trigger':55B 'unauthor':36B 'user':58B 'window':23B","search_c":"'allow':70C 'attack':73C 'base':63C 'buffer':64C 'code':76C 'execut':75C 'heap':62C 'heap-bas':61C 'microsoft':67C 'network':79C 'offic':68C 'outlook':69C 'overflow':65C 'unauthor':72C","cause_entry":null,"cause_path":null,"disclosures_checked_at":null,"first_public_at":"2026-11-10T19:20:41+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-2026-123380","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-123380","severity":null,"published_at":"2026-11-10T19:20:41+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"}