What is CVE-2026-41091?
Improper link resolution before file access ('link following') in Microsoft Defender allows an authorized attacker to elevate privileges locally.
The record classifies CVE-2026-41091 under weakness class CWE-59. Its CVSS v3 base vector states that the flaw requires local access to the host, needs low-privilege credentials, needs no user interaction, and has high impact on confidentiality, integrity, availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 161 days ago.
Severity and exploitation probability
- CVSS v3.1 base score
- 7.8 — HIGH
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C - EPSS (FIRST)
- 0.4% probability of exploitation in the next 30 days, higher than 36.5% of all scored CVEs
- CISA KEV
- Listed since 2026-05-20, federal remediation deadline 2026-06-03 — used in known ransomware campaigns
- Threadlinqs priority
- 10/10 — CISA lists it as used in ransomware, which Threadlinqs scores at the maximum
- Published
- 2026-05-20, last modified 2026-08-10
Is CVE-2026-41091 being exploited?
CISA added CVE-2026-41091 to the Known Exploited Vulnerabilities catalog on 2026-05-20, which means the agency holds evidence of exploitation in the wild; US federal civilian agencies had to remediate it by 2026-06-03 under BOD 22-01. CISA flags the vulnerability as one used in known ransomware campaigns. Weaponised exploit code for CVE-2026-41091 is publicly available. 4 public proof-of-concept repositories are tracked for this identifier. It currently carries a trending score of 32 in the Threadlinqs vulnerability feed.
- 0xBlackash/CVE-2026-41091 (github)
- tc4dy/CVE-2026-41091-PoC-Exploit (github)
- s4m98/RedSun- (github)
- ridhinva/defender-privilege-escalation-scanner (github)
Affected products and versions
- Microsoft: Malware Protection Engine
How to fix CVE-2026-41091
Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-41091. Because CVE-2026-41091 is KEV-listed, US federal civilian agencies were required to apply the vendor fix, or stop using the product, by 2026-06-03. Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.
Threat activity tracking CVE-2026-41091
2 tracked threats in the Threadlinqs corpus reference CVE-2026-41091, either in the campaign’s CVE list or as an indicator on the campaign record.
- NightmareEclipse Coordinated Disclosure Breach Campaign: 9+ Windows Zero-Days (CVE-2026-33825, CVE-2026-41091, CVE-2026-45498, CVE-2026-45585, CVE-2026-45586) Dumped Outside Responsible Disclosure and Weaponized in Real-World Intrusions — CRITICAL · 2026-08-04
- CISA KEV Catalog Adds Seven Vulnerabilities (May 20, 2026) — Microsoft Defender CVE-2026-41091 (EoP) and CVE-2026-45498 (DoS) Headline Active Exploitation Batch — HIGH · 2026-05-21
Sources
Enriched from CVE.org, NVD, FIRST EPSS, CISA KEV, GitHub Security Advisories, public proof-of-concept repositories. Last verified by Threadlinqs on . This product uses the NVD API but is not endorsed or certified by the NVD.