{"id":"CVE-2026-81963","aliases":["EUVD-2026-73889","GHSA-4j4j-2wjq-mxqj"],"status":"published","title":"Windows Update Stack Elevation of Privilege Vulnerability","description":"Improper link resolution before file access ('link following') in Windows Update Stack allows an authorized attacker to elevate privileges locally.","severity":{"version":"3.1","score":7.8,"vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.00393,"percentile":0.33853,"model":"v2026.06.15"},"facts":{"in_kev":true,"known_exploited":true,"public_exploit":true,"fix_available":false},"cwes":["CWE-284","CWE-59"],"published":"2026-09-08T17:19:13Z","modified":"2026-10-31T16:17:44Z","kev":{"date_added":"2026-09-08","due_date":"2026-09-22","required_action":"Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.","known_ransomware_use":"Unknown"},"exploitation":[{"source":"euvd","since":"2026-09-08"},{"source":"kev","since":"2026-09-08"}],"exploits":[{"source":"pocgithub","id":"rsah35404-star/stunning-octo-doodle","title":"rsah35404-star/stunning-octo-doodle","date":"2026-10-19","url":"https://github.com/rsah35404-star/stunning-octo-doodle"}],"products":[{"vendor":"microsoft","product":"windows"},{"vendor":"microsoft","product":"windows 11 version 23h2"},{"vendor":"microsoft","product":"windows 11 version 24h2"},{"vendor":"microsoft","product":"windows 11 version 25h2"},{"vendor":"microsoft","product":"windows 11 version 26h1"},{"vendor":"microsoft","product":"windows server 2025"},{"vendor":"microsoft","product":"windows server 2025 (server core installation)"},{"vendor":"microsoft","product":"windows_11_23h2"},{"vendor":"microsoft","product":"windows_11_24h2"},{"vendor":"microsoft","product":"windows_11_25h2"},{"vendor":"microsoft","product":"windows_11_26h1"},{"vendor":"microsoft","product":"windows_server_2025"}],"references":[{"url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-81963","tags":["vendor-advisory","patch","Patch","Vendor Advisory"]},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-81963","tags":["government-resource","US Government Resource"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-81963"},{"url":"https://github.com/advisories/GHSA-4j4j-2wjq-mxqj"}],"sources":{"cve":[{"id":"CVE-2026-81963","title":"Windows Update Stack Elevation of Privilege Vulnerability","description":"Improper link resolution before file access ('link following') in Windows Update Stack allows an authorized attacker to elevate privileges locally.","status":"published","published":"2026-09-08T17:19:13.121Z","modified":"2026-11-10T21:38:14.835Z","cvss":[{"version":"3.1","score":7.8,"vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C","level":"high","assessor":"cna"}],"cwes":["CWE-59","CWE-284"],"updated_at":"2026-11-10T22:48:54.14451Z"}],"euvd":[{"id":"EUVD-2026-73889","description":"Improper link resolution before file access ('link following') in Windows Update Stack allows an authorized attacker to elevate privileges locally.","status":"published","published":"2026-09-08T17:19:13Z","modified":"2026-11-10T21:38:14Z","cvss":[{"version":"3.1","score":7.8,"vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C","level":"high"}],"exploited_since":"2026-09-08","updated_at":"2026-11-10T23:24:19.311812Z"}],"ghsa":[{"id":"GHSA-4j4j-2wjq-mxqj","title":"Improper link resolution before file access ('link following') in Windows Update Stack allows an...","description":"Improper link resolution before file access ('link following') in Windows Update Stack allows an authorized attacker to elevate privileges locally.","status":"published","published":"2026-09-08T18:33:34Z","modified":"2026-09-08T21:34:09Z","cvss":[{"version":"3.1","score":7.8,"vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","level":"high"}],"cwes":["CWE-59"],"updated_at":"2026-11-02T15:11:35.275364Z"}],"kev":[{"id":"CVE-2026-81963","title":"Microsoft Windows Link Following Vulnerability","description":"Microsoft Windows Update Stack contains a link following vulnerability that allows a local attacker to escalate privileges locally up to SYSTEM.","cwes":["CWE-59","CWE-284"],"kev":{"date_added":"2026-09-08","due_date":"2026-09-22","required_action":"Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.","known_ransomware_use":"Unknown"},"updated_at":"2026-11-02T17:00:15.999436Z"}],"nvd":[{"id":"CVE-2026-81963","description":"Improper link resolution before file access ('link following') in Windows Update Stack allows an authorized attacker to elevate privileges locally.","status":"published","published":"2026-09-08T18:21:00.09Z","modified":"2026-09-09T05:18:17.173Z","cvss":[{"version":"3.1","score":7.8,"vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","level":"high","assessor":"secondary"}],"cwes":["CWE-59","CWE-284"],"updated_at":"2026-11-02T14:12:45.264578Z"}]}}