{"id":"CVE-2026-118721","kind":"vulnerability","aliases":["CVE-2026-118721"],"related":[],"title":"Microsoft Excel: heap buffer overflow lets an attacker run code remotely","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 Excel lets an unauthorized attacker run code over a network. The sources give no further detail on how the file or request is delivered.","severity":"high","cvss":8.8,"epss":null,"exploited":false,"exploited_at":null,"products":[{"name":"Microsoft Office Excel","fixed":[],"affected":"","ecosystem":"vendor"}],"ecosystems":["vendor"],"tags":["excel","microsoft-office","other","windows"],"not_affected_if":[],"how_to_check":"- Check the installed Excel build in Microsoft 365 or Office, unknown for the affected build range.","fix":null,"status":"open","published_at":"2026-11-10T19:19:48+00:00","first_seen_at":"2026-11-10T19:24:54+00:00","triaged_at":"2026-11-10T19:28:19+00:00","updated_at":"2026-11-10T19:28:19+00:00","category":"other","confidence":0.5,"triage":{"at":"2026-11-10T19:28:19Z","model":"claude-haiku-5-5","output":{"fix":"unknown","reach":"network","title":"Microsoft Excel: heap buffer overflow lets an attacker run code remotely","impact":"high","summary":"A heap-based buffer overflow in Microsoft Excel lets an unauthorized attacker run code over a network. The sources give no further detail on how the file or request is delivered.","audience":"businesses","category":"other","nicknames":[],"who_cares":["excel","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":"Confirm affected Excel builds, the triggering file or network path, and the Microsoft fix from the MSRC advisory for CVE-2026-118721.","how_to_check":"- Check the installed Excel build in Microsoft 365 or Office, unknown for the affected build range.\n- unknown, the sources do not say which versions are affected.","plain_action":"","product_name":"Microsoft Office Excel","needs_analyst":true,"not_affected_if":[],"who_is_affected":"Organizations running Microsoft Office Excel. The sources do not say which versions are affected or what user action triggers the flaw, so exposure cannot be confirmed from this data.","user_interaction":"unknown","product_ecosystem":"vendor","needs_special_setup":"unknown","severity_if_unknown":"high"},"cost_usd":0.000694,"input_tokens":4496,"output_tokens":488,"severity_before":"high"},"analyst_status":"queued","analyst_note":"Confirm affected Excel builds, the triggering file or network path, and the Microsoft fix from the MSRC advisory for CVE-2026-118721.","search":"'-118721':14A,17A '-2026':13A,16A 'allow':68C 'attack':8A,39B,71C 'base':30B,61C 'buffer':4A,31B,62C 'code':10A,41B,74C 'cve':12A,15A 'deliv':58B 'detail':50B 'excel':2A,20A,21B,35B,67C 'execut':73C 'file':54B 'give':47B 'heap':3A,29B,60C 'heap-bas':28B,59C 'let':6A,36B 'microsoft':1A,18A,23B,34B,65C 'microsoft-offic':22B 'network':44B,77C 'offic':24B,66C 'office':19A 'overflow':5A,32B,63C 'remot':11A 'request':56B 'run':9A,40B 'sourc':46B 'unauthor':38B,70C 'window':26B","nicknames":[],"mitigations":[],"who_affected":"Organizations running Microsoft Office Excel. The sources do not say which versions are affected or what user action triggers the flaw, so exposure cannot be confirmed from this data.","tier":"B","verified":{},"analyst_revisit_at":null,"fix_status":"none","audience":"businesses","plain_action":null,"pkeys":["microsoftofficeexcel","officeexcel"],"ptokens":["excel","microsoft","office"],"labels":["excel","high","microsoftoffice","other","vendor","windows"],"campaign_type":null,"search_a":"'-118721':14A,17A '-2026':13A,16A 'attack':8A 'buffer':4A 'code':10A 'cve':12A,15A 'excel':2A,20A 'heap':3A 'let':6A 'microsoft':1A,18A 'office':19A 'overflow':5A 'remot':11A 'run':9A","search_b":"'attack':39B 'base':30B 'buffer':31B 'code':41B 'deliv':58B 'detail':50B 'excel':21B,35B 'file':54B 'give':47B 'heap':29B 'heap-bas':28B 'let':36B 'microsoft':23B,34B 'microsoft-offic':22B 'network':44B 'offic':24B 'overflow':32B 'request':56B 'run':40B 'sourc':46B 'unauthor':38B 'window':26B","search_c":"'allow':68C 'attack':71C 'base':61C 'buffer':62C 'code':74C 'excel':67C 'execut':73C 'heap':60C 'heap-bas':59C 'microsoft':65C 'network':77C 'offic':66C 'overflow':63C 'unauthor':70C","cause_entry":null,"cause_path":null,"disclosures_checked_at":null,"first_public_at":"2026-11-10T19:19:48+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-2026-118721","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-118721","severity":null,"published_at":"2026-11-10T19:19:48+00:00","modified_at":"2026-11-10T19:19:48+00:00","first_seen_at":"2026-11-10T19:24:54+00:00","fetched_at":"2026-11-10T19:24:54+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"}