Microsoft Warns of Two Actively Exploited Defender Vulnerabilities

Ravie LakshmananMay 21, 2026Endpoint Security / Vulnerability

Microsoft has disclosed that a privilege escalation and a denial-of-service flaw in Defender has come under active exploitation in the wild.

The former, tracked as CVE-2026-41091, is rated 7.8 on the CVSS scoring system. Successful exploitation of the flaw could allow an attacker to gain SYSTEM privileges.

“Improper link resolution before file access (‘link following’) in Microsoft Defender allows an authorized attacker to elevate privileges locally,” Microsoft said in an advisory.

The second vulnerability under exploitation is CVE-2026-45498 (CVSS score: 4.0), a denial-of-service bug impacting Defender. The two vulnerabilities have been addressed in Microsoft Defender Antimalware Platform versions 1.1.26040.8 and 4.18.26040.7, respectively.

The tech giant noted that systems that have disabled Microsoft Defender are not susceptible to the vulnerability, adding that no action is required to install the update…