Microsoft Defender Privilege Escalation via Symlink Following

CVE-2026-41091 exploits improper link resolution in Microsoft Defender, allowing authorized local users to escalate privileges through symlink (symbolic link) following. This CWE-59 vulnerability is particularly concerning because it targets a foundational security tool—one that defenders rely on to protect systems. The attack requires local access but no special privileges initially, making it attractive to threat actors who have already gained a foothold on Windows systems. With active exploitation confirmed in CISA's Known Exploited Vulnerabilities catalog, this represents an immediate risk to organizations running affected Microsoft Defender versions.

While CVE-2026-41091 doesn't map to specific MITRE ATT&CK techniques in current frameworks, Casky.ai's Claude-powered analysis engine would detect the attack patterns associated with privilege escalation and local file system manipulation. Practitioners using Casky would observe findings related to suspicious symlink creation, unusual file access patterns during Defender operations, and privilege boundary violations—behavioral indicators that Claude's extended reasoning can correlate across 754 mapped security skills. The platform would highlight process execution anomalies and unauthorized elevation attempts that precede successful privilege escalation, enabling detection before full system compromise occurs.