{"id":"CVE-2026-21509","aliases":["EUVD-2026-4666","GHSA-ch84-h92g-mw93"],"status":"published","title":"Microsoft Office Security Feature Bypass Vulnerability","description":"Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.","severity":{"version":"3.1","score":7.8,"vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.70823,"percentile":0.99407,"model":"v2026.06.15"},"facts":{"in_kev":true,"known_exploited":true,"public_exploit":true,"fix_available":false},"cwes":["CWE-807"],"published":"2026-01-26T17:06:35Z","modified":"2026-07-30T20:47:35Z","kev":{"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.","known_ransomware_use":"Unknown"},"exploitation":[{"source":"euvd","since":"2026-01-26"},{"source":"kev","since":"2026-01-26"}],"exploits":[{"source":"pocgithub","id":"kimstars/Ashwesker-CVE-2026-21509","title":"kimstars/Ashwesker-CVE-2026-21509","date":"2026-01-27","url":"https://github.com/kimstars/Ashwesker-CVE-2026-21509"},{"source":"pocgithub","id":"gavz/CVE-2026-21509-PoC","title":"gavz/CVE-2026-21509-PoC","date":"2026-01-29","url":"https://github.com/gavz/CVE-2026-21509-PoC"},{"source":"pocgithub","id":"ksk-itdk/KSK-ITDK-CVE-2026-21509-Mitigation","title":"ksk-itdk/KSK-ITDK-CVE-2026-21509-Mitigation","date":"2026-01-29","url":"https://github.com/ksk-itdk/KSK-ITDK-CVE-2026-21509-Mitigation"},{"source":"pocgithub","id":"SimoesCTT/CTT-NFS-Vortex-RCE","title":"SimoesCTT/CTT-NFS-Vortex-RCE","date":"2026-01-31","url":"https://github.com/SimoesCTT/CTT-NFS-Vortex-RCE"},{"source":"pocgithub","id":"SimoesCTT/SCTT-2026-33-0007-The-OLE-Vortex-Laminar-Bypass-","title":"SimoesCTT/SCTT-2026-33-0007-The-OLE-Vortex-Laminar-Bypass-","date":"2026-01-31","url":"https://github.com/SimoesCTT/SCTT-2026-33-0007-The-OLE-Vortex-Laminar-Bypass-"},{"source":"pocgithub","id":"SimoesCTT/CTT-MICROSOFT-OFFICE-OLE-MANIFOLD-BYPASS-CVE-2026-21509","title":"SimoesCTT/CTT-MICROSOFT-OFFICE-OLE-MANIFOLD-BYPASS-CVE-2026-21509","date":"2026-02-01","url":"https://github.com/SimoesCTT/CTT-MICROSOFT-OFFICE-OLE-MANIFOLD-BYPASS-CVE-2026-21509"},{"source":"pocgithub","id":"decalage2/detect_CVE-2026-21509","title":"decalage2/detect_CVE-2026-21509","date":"2026-02-04","url":"https://github.com/decalage2/detect_CVE-2026-21509"},{"source":"pocgithub","id":"kaizensecurity/CVE-2026-21509","title":"kaizensecurity/CVE-2026-21509","date":"2026-02-05","url":"https://github.com/kaizensecurity/CVE-2026-21509"},{"source":"pocgithub","id":"planetoid/cve-2026-21509-mitigation","title":"planetoid/cve-2026-21509-mitigation","date":"2026-02-11","url":"https://github.com/planetoid/cve-2026-21509-mitigation"},{"source":"pocgithub","id":"suuhm/CVE-2026-21509-handler","title":"suuhm/CVE-2026-21509-handler","date":"2026-03-01","url":"https://github.com/suuhm/CVE-2026-21509-handler"},{"source":"pocgithub","id":"DameDode/CVE-2026-21509-POC","title":"DameDode/CVE-2026-21509-POC","date":"2026-03-12","url":"https://github.com/DameDode/CVE-2026-21509-POC"},{"source":"pocgithub","id":"razureink/cve-2026-21509-office_security_bypass_reproduction","title":"razureink/cve-2026-21509-office_security_bypass_reproduction","date":"2026-07-23","url":"https://github.com/razureink/cve-2026-21509-office_security_bypass_reproduction"}],"products":[{"vendor":"microsoft","product":"365_apps"},{"vendor":"microsoft","product":"microsoft 365 apps for enterprise"},{"vendor":"microsoft","product":"microsoft office 2016"},{"vendor":"microsoft","product":"microsoft office 2019"},{"vendor":"microsoft","product":"microsoft office ltsc 2021"},{"vendor":"microsoft","product":"microsoft office ltsc 2024"},{"vendor":"microsoft","product":"office"},{"vendor":"microsoft","product":"office_long_term_servicing_channel"}],"references":[{"url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21509","tags":["vendor-advisory","patch","Vendor Advisory"]},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-21509","tags":["government-resource","US Government Resource"]},{"url":"https://www.vicarius.io/vsociety/posts/cve-2026-21509-detection-script-microsoft-office-security-feature-bypass-vulnerability","tags":["Third Party Advisory"]},{"url":"https://www.vicarius.io/vsociety/posts/cve-2026-21509-mitigation-script-microsoft-office-security-feature-bypass-vulnerability","tags":["Mitigation","Third Party Advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-21509"},{"url":"https://github.com/advisories/GHSA-ch84-h92g-mw93"}],"sources":{"cve":[{"id":"CVE-2026-21509","title":"Microsoft Office Security Feature Bypass Vulnerability","description":"Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.","status":"published","published":"2026-01-26T17:06:35.512Z","modified":"2026-07-30T20:47:35.007Z","cvss":[{"version":"3.1","score":7.8,"vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C","level":"high","assessor":"cna"}],"cwes":["CWE-807"],"updated_at":"2026-11-02T13:41:42.05254Z"}],"euvd":[{"id":"EUVD-2026-4666","description":"Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.","status":"published","published":"2026-01-26T17:06:35Z","modified":"2026-07-30T20:47:35Z","cvss":[{"version":"3.1","score":7.8,"vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C","level":"high"}],"exploited_since":"2026-01-26","updated_at":"2026-11-02T18:02:26.773248Z"}],"ghsa":[{"id":"GHSA-ch84-h92g-mw93","title":"Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized...","description":"Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.","status":"published","published":"2026-01-26T18:31:31Z","modified":"2026-02-10T15:30:22Z","cvss":[{"version":"3.1","score":7.8,"vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","level":"high"}],"cwes":["CWE-807"],"updated_at":"2026-11-02T15:06:07.19064Z"}],"kev":[{"id":"CVE-2026-21509","title":"Microsoft Office Security Feature Bypass Vulnerability","description":"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.","cwes":["CWE-807"],"kev":{"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.","known_ransomware_use":"Unknown"},"updated_at":"2026-11-02T17:00:15.999436Z"}],"nvd":[{"id":"CVE-2026-21509","description":"Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.","status":"published","published":"2026-01-26T18:16:38.54Z","modified":"2026-06-25T05:16:53.167Z","cvss":[{"version":"3.1","score":7.8,"vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","level":"high","assessor":"secondary"}],"cwes":["CWE-807"],"updated_at":"2026-11-02T14:12:04.769088Z"}]}}