{"id":"CVE-2021-38646","published":"2021-09-15T12:15:15Z","modified":"2026-08-10T19:59:12Z","title":"Microsoft Office Access Connectivity Engine Remote Code Execution Vulnerability","vendor":"Microsoft","product":"Office","tier":"core","eol":null,"description":{"text":"Microsoft Office Access Connectivity Engine Remote Code Execution Vulnerability","provenance":"source","from":"NVD"},"summary":null,"cvss":{"score":7.8,"severity":"HIGH","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","provenance":"source","from":"NVD"},"epss":{"score":0.07987,"percentile":0.94758,"date":"2026-10-31","provenance":"source"},"kev":{"dateAdded":"2022-03-28","dueDate":"2022-04-18","ransomware":true,"requiredAction":"Apply updates per vendor instructions.","notes":"https://nvd.nist.gov/vuln/detail/CVE-2021-38646","provenance":"source"},"vulncheckKev":{"dateAdded":"2022-03-28","exploitedFirstSeen":"2022-03-28","ransomware":true,"evidence":[{"url":"https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json","date":"2022-03-28"},{"url":"https://static.tenable.com/marketing/whitepapers/Whitepaper-Ransomware_Ecosystem.pdf","date":"2022-06-22"}],"evidenceTotal":2,"provenance":"source"},"exploited":true,"otx":null,"cwes":[],"references":[{"url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-38646","tags":["Patch","Vendor Advisory"]},{"url":"https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-38646","tags":["Patch","Vendor Advisory"]},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-38646","tags":["US Government Resource"]}],"techniques":[{"id":"T1204.002","name":"Malicious File","tactics":["execution"],"provenance":"ai","basis":"ai-mapping","bases":["ai-mapping"],"basisDetail":"claude-haiku-5-5: User opens crafted Office file triggering code execution","mappingType":"exploitation_technique","evidence":[{"from":"description","quote":"Microsoft Office Access Connectivity Engine Remote Code Execution Vulnerability","start":0,"end":79}],"model":"claude-haiku-5-5","confidence":"medium","confidenceNote":"AI-mapped from the description (quote-validated, not expert-reviewed)"},{"id":"T1059","name":"Command and Scripting Interpreter","tactics":["execution"],"provenance":"ai","basis":"ai-mapping","bases":["ai-mapping"],"basisDetail":"claude-haiku-5-5: Successful exploitation yields arbitrary code execution","mappingType":"primary_impact","evidence":[{"from":"description","quote":"Microsoft Office Access Connectivity Engine Remote Code Execution Vulnerability","start":0,"end":79}],"model":"claude-haiku-5-5","confidence":"medium","confidenceNote":"AI-mapped from the description (quote-validated, not expert-reviewed)"}],"reports":[],"affected":[],"advisories":[],"euvd":{"id":"EUVD-2021-25085","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2021-25085","exploited":true,"exploitedSince":"2022-03-28","provenance":"source"},"exploits":[],"exploitSources":null,"exploitRefs":[],"flow":[{"stage":"exploitation","techniques":["T1204.002"],"provenance":"ai"},{"stage":"primary","techniques":["T1059"],"provenance":"ai"}],"timeline":[{"date":"2021-09-15","kind":"published","label":"Published (NVD)","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-38646","provenance":"source"},{"date":"2022-03-28","kind":"exploited-reported","label":"Exploitation first reported (VulnCheck KEV evidence)","url":"https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json","provenance":"source"},{"date":"2022-03-28","kind":"kev","label":"Added to CISA KEV (known ransomware use)","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","provenance":"source"},{"date":"2022-03-28","kind":"euvd-exploited","label":"ENISA EUVD: exploited","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2021-25085","provenance":"source"}],"speed":{"daysToPublicExploit":null,"firstExploitFrom":null,"daysToKev":194},"priority":{"score":69.4,"factors":[{"name":"In a KEV catalog","points":35.0,"detail":"listed in CISA KEV and VulnCheck KEV"},{"name":"Recent KEV listing","points":0.0,"detail":"added 1679 days ago"},{"name":"Known ransomware use","points":10.0,"detail":"CISA KEV and VulnCheck KEV: Known"},{"name":"EPSS percentile","points":18.95,"detail":"percentile 0.9476"},{"name":"Named in threat reports","points":0.0,"detail":"0 reports"},{"name":"Public exploit code","points":0.0,"detail":"none found"},{"name":"Mentioned in OTX pulses","points":0.0,"detail":"0 pulses"},{"name":"CVSS severity","points":5.46,"detail":"base score 7.8"},{"name":"End-of-life product","points":0.0,"detail":"supported or unknown"}]}}