{"id":"CVE-2026-41091","kind":"vulnerability","aliases":["CVE-2026-41091"],"related":[],"title":"microsoft malware protection engine: Improper link resolution before file access ('link following') in Microsoft Defender allows an authorized attacker…","description":"Microsoft Defender contains a link following vulnerability that allows an authorized attacker to elevate privileges locally.\n\nCISA 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.","summary":"Microsoft Defender contains a link following flaw that lets a locally authorized attacker elevate privileges on the machine. CISA lists it as actively exploited in the wild.","severity":"high","cvss":7.8,"epss":null,"exploited":true,"exploited_at":"2026-05-20T00:00:00+00:00","products":[{"name":"Microsoft Defender","fixed":[],"affected":"","ecosystem":"vendor"},{"name":"microsoft malware protection engine","fixed":["1.1.26040.8"],"affected":">= 1.1.26030.3008, < 1.1.26040.8","ecosystem":"vendor"}],"ecosystems":["vendor"],"tags":["endpoints","exploited","microsoft-defender","other","windows"],"not_affected_if":["no-local-untrusted-users"],"how_to_check":null,"fix":"Apply the mitigations per Microsoft's vendor instructions referenced by CISA; the sources do not name a patched version.","status":"open","published_at":"2026-05-20T00:00:00+00:00","first_seen_at":"2026-10-23T19:11:51+00:00","triaged_at":"2026-10-23T20:35:39+00:00","updated_at":"2026-10-23T23:44:51+00:00","category":"other","confidence":0.6,"triage":{"at":"2026-10-23T20:35:39Z","model":"claude-haiku-5-5","output":{"fix":"Apply the mitigations per Microsoft's vendor instructions referenced by CISA; the sources do not name a patched version.","summary":"Microsoft Defender contains a link following flaw that lets a locally authorized attacker elevate privileges on the machine. CISA lists it as actively exploited in the wild.","category":"other","who_cares":["windows","microsoft-defender","endpoints"],"confidence":0.6,"analyst_note":"Find the Microsoft advisory for CVE-2026-41091 for affected versions, patched build, and specific mitigation steps; check the CISA KEV entry for the federal due date.","how_to_check":"unknown","needs_analyst":true,"not_affected_if":["no-local-untrusted-users"],"severity_if_unknown":"high"},"cost_usd":0.000339,"input_tokens":2043,"output_tokens":269,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-01':94C '-2026':21A,24A '-41091':22A,25A '22':93C 'access':10A 'action':84C 'activ':61B 'allow':16A,74C 'appli':85C 'applic':91C 'attack':19A,51B,77C 'author':18A,50B,76C 'bod':92C 'cisa':57B,82C 'cloud':97C 'contain':41B,68C 'cve':20A,23A 'defend':15A,36B,40B,67C 'defender':27A 'discontinu':100C 'elev':52B,79C 'endpoint':32B 'engin':4A 'engine':31A 'exploit':33B,62B 'file':9A 'flaw':45B 'follow':12A,44B,71C,90C 'guidanc':95C 'improp':5A 'instruct':89C 'let':47B 'link':6A,11A,43B,70C 'list':58B 'local':49B,81C 'machin':56B 'malwar':2A 'malware':29A 'microsoft':1A,14A,26A,28A,35B,39B,66C 'microsoft-defend':34B 'mitig':86C,106C 'per':87C 'privileg':53B,80C 'product':104C 'protect':3A 'protection':30A 'requir':83C 'resolut':7A 'servic':98C 'unavail':108C 'use':101C 'vendor':88C 'vulner':72C 'wild':65B 'window':38B","nicknames":[],"mitigations":[],"who_affected":null,"tier":null,"verified":{},"analyst_revisit_at":null,"first_public_at":"2026-05-20T00:00:00+00:00","kev":{"dateAdded":"2026-05-20","dueDate":"2026-06-03","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.","knownRansomwareCampaignUse":"Unknown"},"cvss_vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","cvss_by":"secure@microsoft.com","poc_count":0,"sources":[{"source":"kev","external_id":"CVE-2026-41091","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2026-41091","severity":null,"published_at":"2026-05-20T00:00:00+00:00","modified_at":null,"first_seen_at":"2026-10-23T19:11:51+00:00","fetched_at":"2026-10-25T11:39:14+00:00","note":null},{"source":"nvd","external_id":"CVE-2026-41091","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-41091","severity":null,"published_at":"2026-05-20T13:16:29+00:00","modified_at":"2026-07-24T10:10:00+00:00","first_seen_at":"2026-10-23T23:44:51+00:00","fetched_at":"2026-10-23T23:44:51+00:00","note":null}],"documents":[],"notice":"Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}