{"id":"CVE-2026-123378","kind":"vulnerability","aliases":["CVE-2026-123378"],"related":[],"title":"Microsoft Outlook: integer overflow lets an unauthorized attacker run code","description":"Integer overflow or wraparound in Microsoft Office Outlook allows an unauthorized attacker to execute code over a network.","summary":"An integer overflow in Microsoft Office Outlook can be triggered by an unauthorized attacker over the network. The sources say this allows code execution, with a CVSS score of 7.5.","severity":"high","cvss":7.5,"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":"2026-11-10T19:20:41+00:00","first_seen_at":"2026-11-10T19:25:12+00:00","triaged_at":"2026-11-10T19:44:18+00:00","updated_at":"2026-11-10T19:44:18+00:00","category":"package","confidence":0.4,"triage":{"at":"2026-11-10T19:44:18Z","model":"claude-haiku-5-5","output":{"fix":"unknown","reach":"network","title":"Microsoft Outlook: integer overflow lets an unauthorized attacker run code","impact":"high","summary":"An integer overflow in Microsoft Office Outlook can be triggered by an unauthorized attacker over the network. The sources say this allows code execution, with a CVSS score of 7.5.","audience":"everyone","category":"package","nicknames":[],"who_cares":["outlook","microsoft-office","windows"],"confidence":0.4,"fix_status":"unknown","needs_auth":"no","worst_case":"Attacker runs code on the machine running Outlook","analyst_note":"Check Microsoft's security update guide for CVE-2026-123378 for affected builds, fixed versions and whether user interaction (such as opening a message) is needed.","how_to_check":"unknown","plain_action":"Update Microsoft Outlook once Microsoft publishes a fix; the sources do not name a version or setting yet.","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":0.00065,"input_tokens":4498,"output_tokens":401,"severity_before":"high"},"analyst_status":"queued","analyst_note":"Check Microsoft's security update guide for CVE-2026-123378 for affected builds, fixed versions and whether user interaction (such as opening a message) is needed.","search":"'-123378':13A,16A '-2026':12A,15A '7.5':52B 'allow':44B,61C 'attack':8A,36B,64C 'code':10A,45B,67C 'cve':11A,14A 'cvss':49B 'execut':46B,66C 'integ':3A,24B,53C 'let':5A 'microsoft':1A,18B,27B,58C 'microsoft-offic':17B 'network':39B,70C 'offic':19B,28B,59C 'outlook':2A,20B,29B,60C 'overflow':4A,25B,54C 'packag':21B 'run':9A 'say':42B 'score':50B 'sourc':41B 'trigger':32B 'unauthor':7A,35B,63C 'window':22B 'wraparound':56C","nicknames":[],"mitigations":[],"who_affected":null,"tier":"B","verified":{},"analyst_revisit_at":null,"fix_status":"none","audience":"everyone","plain_action":"Update Microsoft Outlook once Microsoft publishes a fix; the sources do not name a version or setting yet.","pkeys":[],"ptokens":[],"labels":["high","microsoftoffice","outlook","package","windows"],"campaign_type":null,"search_a":"'-123378':13A,16A '-2026':12A,15A 'attack':8A 'code':10A 'cve':11A,14A 'integ':3A 'let':5A 'microsoft':1A 'outlook':2A 'overflow':4A 'run':9A 'unauthor':7A","search_b":"'7.5':52B 'allow':44B 'attack':36B 'code':45B 'cvss':49B 'execut':46B 'integ':24B 'microsoft':18B,27B 'microsoft-offic':17B 'network':39B 'offic':19B,28B 'outlook':20B,29B 'overflow':25B 'packag':21B 'say':42B 'score':50B 'sourc':41B 'trigger':32B 'unauthor':35B 'window':22B","search_c":"'allow':61C 'attack':64C 'code':67C 'execut':66C 'integ':53C 'microsoft':58C 'network':70C 'offic':59C 'outlook':60C 'overflow':54C 'unauthor':63C 'wraparound':56C","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:H/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-2026-123378","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-123378","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"}