{"id":"CVE-2026-41091","published":"2026-05-20T13:16:29Z","modified":"2026-07-24T10:10:00Z","title":"Microsoft Defender Link Following Vulnerability","vendor":"Microsoft","product":"Defender","tier":"core","eol":null,"description":{"text":"Improper link resolution before file access ('link following') in Microsoft Defender allows an authorized attacker to elevate privileges locally.","provenance":"source","from":"NVD"},"summary":{"text":"A link following flaw in Microsoft Defender, classified as improper link resolution before file access, allows a local user to act on files through symbolic or similar links before they are accessed. An attacker needs an existing low-privilege authorized account on the local system and requires no user interaction to exploit it, allowing privilege escalation.","provenance":"ai","model":"claude-haiku-5-5","generatedAt":"2026-10-30T13:36:25Z"},"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":0.08202,"percentile":0.9487,"date":"2026-10-30","provenance":"source"},"kev":{"dateAdded":"2026-05-20","dueDate":"2026-06-03","ransomware":false,"requiredAction":"Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.","notes":"https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2026-41091 ; https://nvd.nist.gov/vuln/detail/CVE-2026-41091","provenance":"source"},"vulncheckKev":{"dateAdded":"2026-05-19","exploitedFirstSeen":"2026-05-19","ransomware":false,"evidence":[{"url":"https://api.msrc.microsoft.com/cvrf/v3.0/cvrf/2026-May","date":"2026-05-19"},{"url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-41091","date":"2026-05-19"},{"url":"https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json","date":"2026-05-20"},{"url":"https://www.recordedfuture.com/blog/june-2026-cve-landscape","date":"2026-07-10"}],"evidenceTotal":4,"provenance":"source"},"exploited":true,"otx":{"pulseCount":50,"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"}],"references":[{"url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-41091","tags":["Vendor Advisory"]},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-41091","tags":["Third Party Advisory","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":85,"end":144}],"model":"claude-haiku-5-5","confidence":"medium","confidenceNote":"AI-mapped from the description (quote-validated, not expert-reviewed)"},{"id":"T1548","name":"Abuse Elevation Control Mechanism","tactics":["privilege-escalation"],"provenance":"ai","basis":"ai-mapping","bases":["ai-mapping"],"basisDetail":"claude-haiku-5-5: Abuses link resolution to gain elevated access","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-2026-31101","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-31101","exploited":true,"exploitedSince":"2026-05-20","provenance":"source"},"exploits":[],"exploitSources":{"pocGithub":{"count":4,"skipped":0,"earliest":"2026-05-21","earliestUrl":"https://github.com/0xBlackash/CVE-2026-41091","repos":[{"name":"0xBlackash/CVE-2026-41091","url":"https://github.com/0xBlackash/CVE-2026-41091","stars":12,"created":"2026-05-21"},{"name":"tc4dy/CVE-2026-41091-PoC-Exploit","url":"https://github.com/tc4dy/CVE-2026-41091-PoC-Exploit","stars":5,"created":"2026-06-20"},{"name":"s4m98/RedSun-","url":"https://github.com/s4m98/RedSun-","stars":1,"created":"2026-08-09"},{"name":"ridhinva/defender-privilege-escalation-scanner","url":"https://github.com/ridhinva/defender-privilege-escalation-scanner","stars":0,"created":"2026-05-22"}]},"first":{"date":"2026-05-21","source":"PoC-in-GitHub","url":"https://github.com/0xBlackash/CVE-2026-41091"},"provenance":"source"},"exploitRefs":[],"flow":[{"stage":"exploitation","techniques":["T1068"],"provenance":"ai"},{"stage":"primary","techniques":["T1548"],"provenance":"ai"}],"timeline":[{"date":"2026-05-19","kind":"exploited-reported","label":"Exploitation 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listing","points":5.0,"detail":"added 165 days ago"},{"name":"Known ransomware use","points":0.0,"detail":"not known"},{"name":"EPSS percentile","points":18.97,"detail":"percentile 0.9487"},{"name":"Named in threat reports","points":0.0,"detail":"0 reports"},{"name":"Public exploit code","points":5.0,"detail":"4 PoC-in-GitHub repos"},{"name":"Mentioned in OTX pulses","points":3.0,"detail":"50 pulses"},{"name":"CVSS severity","points":5.46,"detail":"base score 7.8"},{"name":"End-of-life product","points":0.0,"detail":"supported or unknown"}]}}