{"id":"CVE-2026-123383","kind":"vulnerability","aliases":["CVE-2026-123383"],"related":[],"title":"Microsoft Outlook: heap buffer overflow lets a remote 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 reach code execution over a network. The NVD entry gives a CVSS score of 8.8 and does not describe the trigger in detail.","severity":"high","cvss":8.8,"epss":null,"exploited":false,"exploited_at":null,"products":[{"name":"Microsoft Office Outlook","fixed":[],"affected":"","ecosystem":"vendor"}],"ecosystems":["vendor"],"tags":["microsoft-office","outlook","package","windows"],"not_affected_if":[],"how_to_check":"- Check the installed Outlook build in Microsoft 365 or Office version settings, as the sources do not name affected builds.","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":"2026-11-10T19:26:24+00:00","updated_at":"2026-11-10T19:26:24+00:00","category":"package","confidence":0.5,"triage":{"at":"2026-11-10T19:26:24Z","model":"claude-haiku-5-5","output":{"fix":"unknown","reach":"network","title":"Microsoft Outlook: heap buffer overflow lets a remote attacker run code","impact":"high","summary":"A heap-based buffer overflow in Microsoft Office Outlook lets an unauthorized attacker reach code execution over a network. The NVD entry gives a CVSS score of 8.8 and does not describe the trigger in detail.","audience":"businesses","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 victim's machine over the network","analyst_note":"Find the affected Outlook builds and Microsoft's patch details at https://nvd.nist.gov/vuln/detail/CVE-2026-123383 and the Microsoft Security Response Center.","how_to_check":"- Check the installed Outlook build in Microsoft 365 or Office version settings, as the sources do not name affected builds.\n- unknown for specific commands or files, as the sources do not say.","plain_action":"","product_name":"Microsoft Office Outlook","needs_analyst":true,"not_affected_if":[],"who_is_affected":"Organizations running Microsoft Office Outlook are likely exposed, since the flaw is reachable over a network without authentication. The sources do not name affected versions or the exact trigger, so the exposed configurations are unknown.","user_interaction":"unknown","product_ecosystem":"vendor","needs_special_setup":"unknown","severity_if_unknown":"high"},"cost_usd":0.000723,"input_tokens":4498,"output_tokens":547,"severity_before":"high"},"analyst_status":"queued","analyst_note":"Find the affected Outlook builds and Microsoft's patch details at https://nvd.nist.gov/vuln/detail/CVE-2026-123383 and the Microsoft Security Response Center.","search":"'-123383':14A,17A '-2026':13A,16A '8.8':55B 'allow':73C 'attack':9A,40B,76C 'base':30B,66C 'buffer':4A,31B,67C 'code':11A,42B,79C 'cve':12A,15A 'cvss':52B 'describ':59B 'detail':63B 'entri':49B 'execut':43B,78C 'give':50B 'heap':3A,29B,65C 'heap-bas':28B,64C 'let':6A,37B 'microsoft':1A,18A,22B,34B,70C 'microsoft-offic':21B 'network':46B,82C 'nvd':48B 'offic':23B,35B,71C 'office':19A 'outlook':2A,20A,24B,36B,72C 'overflow':5A,32B,68C 'packag':25B 'reach':41B 'remot':8A 'run':10A 'score':53B 'trigger':61B 'unauthor':39B,75C 'window':26B","nicknames":[],"mitigations":[],"who_affected":"Organizations running Microsoft Office Outlook are likely exposed, since the flaw is reachable over a network without authentication. The sources do not name affected versions or the exact trigger, so the exposed configurations are unknown.","tier":"B","verified":{},"analyst_revisit_at":null,"fix_status":"none","audience":"businesses","plain_action":null,"pkeys":["microsoftofficeoutlook","officeoutlook"],"ptokens":["microsoft","office","outlook"],"labels":["high","microsoftoffice","outlook","package","vendor","windows"],"campaign_type":null,"search_a":"'-123383':14A,17A '-2026':13A,16A 'attack':9A 'buffer':4A 'code':11A 'cve':12A,15A 'heap':3A 'let':6A 'microsoft':1A,18A 'office':19A 'outlook':2A,20A 'overflow':5A 'remot':8A 'run':10A","search_b":"'8.8':55B 'attack':40B 'base':30B 'buffer':31B 'code':42B 'cvss':52B 'describ':59B 'detail':63B 'entri':49B 'execut':43B 'give':50B 'heap':29B 'heap-bas':28B 'let':37B 'microsoft':22B,34B 'microsoft-offic':21B 'network':46B 'nvd':48B 'offic':23B,35B 'outlook':24B,36B 'overflow':32B 'packag':25B 'reach':41B 'score':53B 'trigger':61B 'unauthor':39B 'window':26B","search_c":"'allow':73C 'attack':76C 'base':66C 'buffer':67C 'code':79C 'execut':78C 'heap':65C 'heap-bas':64C 'microsoft':70C 'network':82C 'offic':71C 'outlook':72C 'overflow':68C 'unauthor':75C","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-2026-123383","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-123383","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"}