{"id":"CVE-2026-81963","published":"2026-09-08T18:21:00Z","modified":"2026-09-09T05:18:17Z","title":"Microsoft Windows Link Following Vulnerability","vendor":"Microsoft","product":"Windows","tier":"core","eol":null,"description":{"text":"Improper link resolution before file access ('link following') in Windows Update Stack allows an authorized attacker to elevate privileges locally.","provenance":"source","from":"NVD"},"summary":{"text":"A link-following flaw in the Windows Update Stack component of Microsoft Windows allows improper link resolution before file access. An attacker who already holds low-privilege, authorized local access can exploit it to elevate privileges, with no user interaction required.","provenance":"ai","model":"claude-haiku-5-5","generatedAt":"2026-10-23T07:15:05Z"},"cvss":{"score":7.8,"severity":"HIGH","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","provenance":"source","from":"NVD"},"epss":{"score":0.00393,"percentile":0.33518,"date":"2026-10-30","provenance":"source"},"kev":{"dateAdded":"2026-09-08","dueDate":"2026-09-22","ransomware":false,"requiredAction":"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.","notes":"https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2026-81963 ; BOD 26-04: https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk ; Forensics Triage Requirements: https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk ; https://nvd.nist.gov/vuln/detail/CVE-2026-81963","provenance":"source"},"vulncheckKev":{"dateAdded":"2026-09-08","exploitedFirstSeen":"2026-09-08","ransomware":false,"evidence":[{"url":"https://api.msrc.microsoft.com/cvrf/v3.0/cvrf/2026-Sep","date":"2026-09-08"},{"url":"https://euvd.enisa.europa.eu/enisa/EUVD-2026-73889","date":"2026-09-08"},{"url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-81963","date":"2026-09-08"},{"url":"https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json","date":"2026-09-08"}],"evidenceTotal":4,"provenance":"source"},"exploited":true,"otx":{"pulseCount":31,"pulses":[{"name":"Actively_Exploited_Kev | Oct 31, 2026","url":"https://otx.alienvault.com/pulse/6ae4aefab0c2191cecd41862","created":"2026-10-30"},{"name":"Actively_Exploited_Kev | Oct 30, 2026","url":"https://otx.alienvault.com/pulse/6ae35d889ea92b4ce19c2680","created":"2026-10-29"},{"name":"Actively_Exploited_Kev | Oct 29, 2026","url":"https://otx.alienvault.com/pulse/6ae20c1db17e7057ae7d9ad1","created":"2026-10-28"},{"name":"Actively_Exploited_Kev | Oct 28, 2026","url":"https://otx.alienvault.com/pulse/6ae0ba7e0e2a97ff7b218819","created":"2026-10-27"},{"name":"Actively_Exploited_Kev | Oct 27, 2026","url":"https://otx.alienvault.com/pulse/6adf68b85c3e852f3c111d18","created":"2026-10-26"},{"name":"Actively_Exploited_Kev | Oct 24, 2026","url":"https://otx.alienvault.com/pulse/6adb740e397c3ad4799aa4cd","created":"2026-10-23"},{"name":"Actively_Exploited_Kev | Oct 23, 2026","url":"https://otx.alienvault.com/pulse/6ada236fcfba2dfa730ea482","created":"2026-10-22"},{"name":"Actively_Exploited_Kev | Oct 22, 2026","url":"https://otx.alienvault.com/pulse/6ad8d33a077cbb5cab524d80","created":"2026-10-21"},{"name":"Actively_Exploited_Kev | Oct 21, 2026","url":"https://otx.alienvault.com/pulse/6ad78130c4d1ac2be83a8b6d","created":"2026-10-20"},{"name":"Actively_Exploited_Kev | Oct 20, 2026","url":"https://otx.alienvault.com/pulse/6ad62f63c24a405a3423cc13","created":"2026-10-19"}],"provenance":"machine"},"cwes":[{"id":"CWE-59","name":"Improper Link Resolution Before File Access"},{"id":"CWE-284","name":"Improper Access Control"}],"references":[{"url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-81963","tags":["Patch","Vendor Advisory"]},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-81963","tags":["US Government Resource"]}],"techniques":[{"id":"T1068","name":"Exploitation for Privilege Escalation","tactics":["privilege-escalation"],"provenance":"ai","basis":"ai-mapping","bases":["ai-mapping"],"basisDetail":"claude-haiku-5-5: local privilege escalation via link following","mappingType":"exploitation_technique","evidence":[{"from":"description","quote":"allows an authorized attacker to elevate privileges locally","start":87,"end":146}],"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: link following enables file-based code execution","mappingType":"primary_impact","evidence":[{"from":"description","quote":"Improper link resolution before file access ('link following')","start":0,"end":62}],"model":"claude-haiku-5-5","confidence":"medium","confidenceNote":"AI-mapped from the description (quote-validated, not expert-reviewed)"}],"reports":[],"affected":[],"advisories":[],"euvd":{"id":"EUVD-2026-73889","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-73889","exploited":true,"exploitedSince":"2026-09-08","provenance":"source"},"exploits":[],"exploitSources":{"pocGithub":{"count":1,"skipped":0,"earliest":"2026-10-19","earliestUrl":"https://github.com/rsah35404-star/stunning-octo-doodle","repos":[{"name":"rsah35404-star/stunning-octo-doodle","url":"https://github.com/rsah35404-star/stunning-octo-doodle","stars":0,"created":"2026-10-19"}]},"first":{"date":"2026-10-19","source":"PoC-in-GitHub","url":"https://github.com/rsah35404-star/stunning-octo-doodle"},"provenance":"source"},"exploitRefs":[],"flow":[{"stage":"exploitation","techniques":["T1068"],"provenance":"ai"},{"stage":"primary","techniques":["T1059"],"provenance":"ai"}],"timeline":[{"date":"2026-09-08","kind":"published","label":"Published (NVD)","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-81963","provenance":"source"},{"date":"2026-09-08","kind":"exploited-reported","label":"Exploitation first reported (VulnCheck KEV evidence)","url":"https://api.msrc.microsoft.com/cvrf/v3.0/cvrf/2026-Sep","provenance":"source"},{"date":"2026-09-08","kind":"kev","label":"Added to CISA KEV","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","provenance":"source"},{"date":"2026-09-08","kind":"euvd-exploited","label":"ENISA EUVD: exploited","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-73889","provenance":"source"},{"date":"2026-10-19","kind":"exploit-public","label":"First public exploit: PoC-in-GitHub","url":"https://github.com/rsah35404-star/stunning-octo-doodle","provenance":"source"}],"speed":{"daysToPublicExploit":41,"firstExploitFrom":"PoC-in-GitHub","daysToKev":0},"priority":{"score":65.2,"factors":[{"name":"In a KEV catalog","points":35.0,"detail":"listed in CISA KEV and VulnCheck KEV"},{"name":"Recent KEV listing","points":10.0,"detail":"added 53 days ago"},{"name":"Known ransomware use","points":0.0,"detail":"not known"},{"name":"EPSS percentile","points":6.7,"detail":"percentile 0.3352"},{"name":"Named in threat reports","points":0.0,"detail":"0 reports"},{"name":"Public exploit code","points":5.0,"detail":"1 PoC-in-GitHub repo"},{"name":"Mentioned in OTX pulses","points":3.0,"detail":"31 pulses"},{"name":"CVSS severity","points":5.46,"detail":"base score 7.8"},{"name":"End-of-life product","points":0.0,"detail":"supported or unknown"}]},"lineage":{"familyId":"fam-class-microsoft-windows-cwe-59"}}