CVE-2026-41091: Microsoft Defender privilege escalation via improper link resolution

CVE-2026-41091 · Severity: critical · CVSS 7.8 · Exploited in the wild · Published 2026-05-20

Microsoft Defender, the built-in security and antivirus suite for Windows, contains a vulnerability that could allow a user with limited access to gain full administrative control over a system. By exploiting how the software handles file shortcuts, an attacker can trick the system into modifying or accessing protected files. This flaw has been reported as being actively exploited in the wild, posing a significant risk to system integrity and data confidentiality.

Technologies: Microsoft Defender. Vendors: Microsoft.

Quick answers

Is CVE-2026-41091 exploited in the wild?
Yes. CVE-2026-41091 is known to be exploited in the wild, first recorded on 20 May 2026. Treat it as urgent.
How severe is CVE-2026-41091?
Critical severity, with a CVSS score of 7.8, published 20 May 2026.
Which products and versions are affected?
Microsoft Defender.
Is there a fix for CVE-2026-41091?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-41091 attacked?
It is attacked with local access, in an operating system.
Am I affected by CVE-2026-41091?
Check whether you run Microsoft Defender. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A link following vulnerability (CWE-59) exists in Microsoft Defender due to improper link resolution before file access. A local attacker with low privileges can exploit this by creating symbolic links or junctions that point to sensitive system files, which the Defender service may then interact with at a higher privilege level. Successful exploitation allows the attacker to achieve full SYSTEM-level privileges, leading to complete compromise of the affected host. This vulnerability is reportedly being exploited in the wild and requires a local presence on the target machine.

Affected products

  • Microsoft Defender

Timeline

  • 2026-05-20: disclosed
  • 2026-05-20: advisory
  • 2026-05-20: exploited: Reported as exploited in the wild at time of disclosure.

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