{"schema":"threatline.record/2","record":{"id":"CVE-2026-21509","aliases":[],"summary":"Microsoft Office Security Feature Bypass Vulnerability","details":"Microsoft Office contains a security feature bypass vulnerability in which reliance on untrusted inputs in a security decision in Microsoft Office could allow an unauthorized attacker to bypass a security feature locally. Some of the impacted product(s) could be end-of-life (EoL) and/or end-of-service (EoS). Users are advised to discontinue use and/or transition to a supported version.","categories":["Applications & CMS"],"product":"Office","vendor":"Microsoft","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-21509","source_modified_at":"2026-07-30T20:47:35.007Z","fetched_at":"2026-10-23T18:42:43.628194Z","product":"Microsoft 365 Apps for Enterprise","vendor":"Microsoft","versions":[{"version":"16.0.1","lessThan":"https://aka.ms/OfficeSecurityReleases","versionType":"custom","status":"affected"}],"defaultStatus":null},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-21509","source_modified_at":"2026-07-30T20:47:35.007Z","fetched_at":"2026-10-23T18:42:43.628194Z","product":"Microsoft Office 2016","vendor":"Microsoft","versions":[{"version":"16.0.0","lessThan":"16.0.5539.1001","versionType":"custom","status":"affected"}],"defaultStatus":null},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-21509","source_modified_at":"2026-07-30T20:47:35.007Z","fetched_at":"2026-10-23T18:42:43.628194Z","product":"Microsoft Office 2019","vendor":"Microsoft","versions":[{"version":"19.0.0","lessThan":"16.0.10417.20095","versionType":"custom","status":"affected"}],"defaultStatus":null},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-21509","source_modified_at":"2026-07-30T20:47:35.007Z","fetched_at":"2026-10-23T18:42:43.628194Z","product":"Microsoft Office LTSC 2021","vendor":"Microsoft","versions":[{"version":"16.0.1","lessThan":"https://aka.ms/OfficeSecurityReleases","versionType":"custom","status":"affected"}],"defaultStatus":null},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-21509","source_modified_at":"2026-07-30T20:47:35.007Z","fetched_at":"2026-10-23T18:42:43.628194Z","product":"Microsoft Office LTSC 2024","vendor":"Microsoft","versions":[{"version":"16.0.0","lessThan":"https://aka.ms/OfficeSecurityReleases","versionType":"custom","status":"affected"}],"defaultStatus":null}],"fixed_versions":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-21509","source_modified_at":"2026-07-30T20:47:35.007Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"name":"Microsoft Office 2016","ecosystem":null},"version":"16.0.5539.1001","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-21509","source_modified_at":"2026-07-30T20:47:35.007Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"name":"Microsoft Office 2019","ecosystem":null},"version":"16.0.10417.20095","basis":"first unaffected version stated in the CVE record"}],"cvss":7.8,"severity":"High","kev":{"listed":true,"date_added":"2026-01-26","due_date":"2026-02-16","required_action":"Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.","ransomware_campaign_use":"Unknown"},"epss":{"probability":0.70795,"percentile":0.99401,"score_date":"2026-10-23"},"published_at":"2026-01-26T17:06:35.512Z","modified_at":"2026-07-30T20:47:35.007Z","provenance":[{"source":"CISA KEV","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23T17:00:09.9001Z"},{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-21509","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-07-30T20:47:35.007Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-21509","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23"}],"sources":["CISA KEV","CVE List","EPSS"],"references":[{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-21509","source":"CISA KEV"},{"source":"CVE List","url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21509","tags":["vendor-advisory","patch"]},{"source":"CVE List","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-21509","tags":["government-resource"]},{"source":"CVE List","url":"https://www.vicarius.io/vsociety/posts/cve-2026-21509-detection-script-microsoft-office-security-feature-bypass-vulnerability"},{"source":"CVE List","url":"https://www.vicarius.io/vsociety/posts/cve-2026-21509-mitigation-script-microsoft-office-security-feature-bypass-vulnerability"}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"cve_state":"PUBLISHED","cvss_source":"CVE List","ssvc":{"exploitation":"active","automatable":"no","technical_impact":"total","assessed_at":"2026-01-26T00:00:00+00:00"},"classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":"product","confidence":"heuristic","reviewed":false},"change_timestamp":"2026-07-30T20:47:35.007Z","content_hash":"17c3ae9071fd179e64b1ea832267d59e3c02af2877a03ca9504ac3291b9970fc"}}