{"id":"CVE-2026-123384","kind":"vulnerability","aliases":["CVE-2026-123384"],"related":[],"title":"Microsoft Outlook: heap overflow lets an unauthenticated attacker run code remotely","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. Sources report CVSS 8.8 (high) and no known exploitation in the wild.","severity":"high","cvss":8.8,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["microsoft-office","outlook","vendor","windows"],"not_affected_if":[],"how_to_check":"- Open Outlook and check the installed build under File > Account > About Outlook\n- Compare the build with Microsoft's security update guide entry for CVE-2026-123384","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":"2026-11-10T19:26:23+00:00","updated_at":"2026-11-10T19:26:23+00:00","category":"vendor","confidence":0.4,"triage":{"at":"2026-11-10T19:26:23Z","model":"claude-haiku-5-5","output":{"fix":"unknown","reach":"network","title":"Microsoft Outlook: heap overflow lets an unauthenticated attacker run code remotely","impact":"high","summary":"A heap-based buffer overflow in Microsoft Office Outlook lets an unauthorized attacker execute code over a network. Sources report CVSS 8.8 (high) and no known exploitation in the wild.","audience":"businesses","category":"vendor","nicknames":[],"who_cares":["outlook","microsoft-office","windows"],"confidence":0.4,"fix_status":"unknown","needs_auth":"no","worst_case":"Attacker runs code on the machine over the network","analyst_note":"Pull Microsoft's security update guide entry for CVE-2026-123384 to confirm affected Outlook builds, the fixed build, and whether preview pane or message opening is required.","how_to_check":"- Open Outlook and check the installed build under File > Account > About Outlook\n- Compare the build with Microsoft's security update guide entry for CVE-2026-123384\n- unknown","plain_action":"","product_name":"","needs_analyst":true,"not_affected_if":[],"who_is_affected":"unknown","user_interaction":"unknown","product_ecosystem":"","needs_special_setup":"unknown","severity_if_unknown":"high"},"cost_usd":0.000677,"input_tokens":4498,"output_tokens":455,"severity_before":"high"},"analyst_status":"queued","analyst_note":"Pull Microsoft's security update guide entry for CVE-2026-123384 to confirm affected Outlook builds, the fixed build, and whether preview pane or message opening is required.","search":"'-123384':14A,17A '-2026':13A,16A '8.8':46B 'allow':64C 'attack':8A,37B,67C 'base':27B,57C 'buffer':28B,58C 'code':10A,39B,70C 'cve':12A,15A 'cvss':45B 'execut':38B,69C 'exploit':51B 'heap':3A,26B,56C 'heap-bas':25B,55C 'high':47B 'known':50B 'let':5A,34B 'microsoft':1A,19B,31B,61C 'microsoft-offic':18B 'network':42B,73C 'offic':20B,32B,62C 'outlook':2A,21B,33B,63C 'overflow':4A,29B,59C 'remot':11A 'report':44B 'run':9A 'sourc':43B 'unauthent':7A 'unauthor':36B,66C 'vendor':22B 'wild':54B 'window':23B","nicknames":[],"mitigations":[],"who_affected":null,"tier":"B","verified":{},"analyst_revisit_at":null,"fix_status":"none","audience":"businesses","plain_action":null,"pkeys":[],"ptokens":[],"labels":["high","microsoftoffice","outlook","vendor","windows"],"campaign_type":null,"search_a":"'-123384':14A,17A '-2026':13A,16A 'attack':8A 'code':10A 'cve':12A,15A 'heap':3A 'let':5A 'microsoft':1A 'outlook':2A 'overflow':4A 'remot':11A 'run':9A 'unauthent':7A","search_b":"'8.8':46B 'attack':37B 'base':27B 'buffer':28B 'code':39B 'cvss':45B 'execut':38B 'exploit':51B 'heap':26B 'heap-bas':25B 'high':47B 'known':50B 'let':34B 'microsoft':19B,31B 'microsoft-offic':18B 'network':42B 'offic':20B,32B 'outlook':21B,33B 'overflow':29B 'report':44B 'sourc':43B 'unauthor':36B 'vendor':22B 'wild':54B 'window':23B","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":"2026-11-10T19:20:41+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-2026-123384","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-123384","severity":null,"published_at":"2026-11-10T19:20:41+00:00","modified_at":"2026-11-10T19:20:42+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"}