{"id":"CVE-2026-118299","kind":"vulnerability","aliases":["CVE-2026-118299"],"related":[],"title":"Microsoft Excel: heap overflow lets an attacker run code over a network","description":"Heap-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to execute code over a network.","summary":"A heap-based buffer overflow in Microsoft Office Excel lets an unauthorized attacker execute code over a network. The sources give no further detail on how a victim is reached.","severity":"high","cvss":8.8,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["excel","microsoft-office","other","windows"],"not_affected_if":[],"how_to_check":"- Open Excel and check the version under File > Account (or About Excel) against the Microsoft security update guide","fix":null,"status":"open","published_at":"2026-11-10T19:19:43+00:00","first_seen_at":"2026-11-10T19:24:52+00:00","triaged_at":"2026-11-10T19:29:54+00:00","updated_at":"2026-11-10T19:29:54+00:00","category":"other","confidence":0.4,"triage":{"at":"2026-11-10T19:29:54Z","model":"claude-haiku-5-5","output":{"fix":"unknown","reach":"network","title":"Microsoft Excel: heap overflow lets an attacker run code over a network","impact":"high","summary":"A heap-based buffer overflow in Microsoft Office Excel lets an unauthorized attacker execute code over a network. The sources give no further detail on how a victim is reached.","audience":"businesses","category":"other","nicknames":[],"who_cares":["excel","microsoft-office","windows"],"confidence":0.4,"fix_status":"unknown","needs_auth":"unknown","worst_case":"code runs on the victim's machine with attacker control","analyst_note":"Check the Microsoft Security Update Guide entry for CVE-2026-118299 for affected builds, fixed versions and whether user interaction is required.","how_to_check":"- Open Excel and check the version under File > Account (or About Excel) against the Microsoft security update guide\n- unknown","plain_action":"","product_name":"","needs_analyst":true,"not_affected_if":[],"who_is_affected":"Organizations running Microsoft Office Excel are the likely exposure; the sources do not name affected builds or whether opening a file is enough to trigger it. unknown","user_interaction":"unknown","product_ecosystem":"","needs_special_setup":"unknown","severity_if_unknown":"high"},"cost_usd":0.000668,"input_tokens":4496,"output_tokens":437,"severity_before":"high"},"analyst_status":"queued","analyst_note":"Check the Microsoft Security Update Guide entry for CVE-2026-118299 for affected builds, fixed versions and whether user interaction is required.","search":"'-118299':15A,18A '-2026':14A,17A 'allow':65C 'attack':7A,38B,68C 'base':28B,58C 'buffer':29B,59C 'code':9A,40B,71C 'cve':13A,16A 'detail':49B 'excel':2A,19B,34B,64C 'execut':39B,70C 'give':46B 'heap':3A,27B,57C 'heap-bas':26B,56C 'let':5A,35B 'microsoft':1A,21B,32B,62C 'microsoft-offic':20B 'network':12A,43B,74C 'offic':22B,33B,63C 'overflow':4A,30B,60C 'reach':55B 'run':8A 'sourc':45B 'unauthor':37B,67C 'victim':53B 'window':24B","nicknames":[],"mitigations":[],"who_affected":"Organizations running Microsoft Office Excel are the likely exposure; the sources do not name affected builds or whether opening a file is enough to trigger it. unknown","tier":"B","verified":{},"analyst_revisit_at":null,"fix_status":"none","audience":"businesses","plain_action":null,"pkeys":[],"ptokens":[],"labels":["excel","high","microsoftoffice","other","windows"],"campaign_type":null,"search_a":"'-118299':15A,18A '-2026':14A,17A 'attack':7A 'code':9A 'cve':13A,16A 'excel':2A 'heap':3A 'let':5A 'microsoft':1A 'network':12A 'overflow':4A 'run':8A","search_b":"'attack':38B 'base':28B 'buffer':29B 'code':40B 'detail':49B 'excel':19B,34B 'execut':39B 'give':46B 'heap':27B 'heap-bas':26B 'let':35B 'microsoft':21B,32B 'microsoft-offic':20B 'network':43B 'offic':22B,33B 'overflow':30B 'reach':55B 'sourc':45B 'unauthor':37B 'victim':53B 'window':24B","search_c":"'allow':65C 'attack':68C 'base':58C 'buffer':59C 'code':71C 'excel':64C 'execut':70C 'heap':57C 'heap-bas':56C 'microsoft':62C 'network':74C 'offic':63C 'overflow':60C 'unauthor':67C","cause_entry":null,"cause_path":null,"disclosures_checked_at":null,"first_public_at":"2026-11-10T19:19:43+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-2026-118299","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-118299","severity":null,"published_at":"2026-11-10T19:19:43+00:00","modified_at":"2026-11-10T19:19:43+00:00","first_seen_at":"2026-11-10T19:24:52+00:00","fetched_at":"2026-11-10T19:24:52+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"}