6 min read
By: RedLegg's Cyber Threat Intelligence Team
About:
CVE-2026-33825 is a high-severity elevation of privilege vulnerability in Microsoft Defender caused by insufficient granularity of access control. The flaw allows an attacker with local access to elevate privileges on the affected system.
Exploitation requires prior access, but once achieved, attackers may gain elevated permissions, access sensitive data, modify security configurations, and interfere with endpoint protection mechanisms. This can enable persistence and deeper compromise of the affected device.
Public proof-of-concept code is available, and exploitation has been observed in the wild prior to patch release.
RedLegg will occasionally communicate vulnerabilities released outside the usual release schedule to provide additional value to our customers. These emergency bulletins describe vulnerabilities or threats we classify as the highest severity level and warrant out-of-band emergency patching or mitigation action.
VULNERABILITIES
Elevation of Privilege Vulnerability in Microsoft Defender
Identifier: CVE-2026-33825
CVSS Score: 7.8 (High, CVSS v3.1)
PoC or Exploitation:
Public proof-of-concept code is available and exploitation has been observed in the wild prior to patch release.
Update/ Patch:
Microsoft has published a security advisory for CVE-2026-33825. Organizations should apply the relevant Microsoft Defender security update or platform update referenced in Microsoft's advisory.
Microsoft security update guidance:
Affected version: Version 4.18.26020.6
Fixed version: Version 4.18.26030.3011
Description:
CVE-2026-33825 is an elevation of privilege vulnerability in Microsoft Defender. The vulnerability is caused by insufficient granularity of access control.
An authorized attacker with local access can exploit this vulnerability to elevate privileges on the affected system.
Successful exploitation could allow an attacker to gain elevated privileges, access sensitive data, modify security settings, interfere with endpoint protections, and further entrench themselves on the affected device.
Mitigation Recommendation:
Immediately apply the Microsoft security updates addressing CVE-2026-33825.
Prioritize patching endpoints that handle sensitive workloads or privileged user activity.
Enforce least privilege controls and restrict unnecessary local administrative access.
Monitor endpoints for suspicious privilege escalation behavior, unexpected changes to Microsoft Defender settings, or attempts to tamper with security controls.
Use endpoint detection and response telemetry to investigate unusual local activity that may indicate post-compromise exploitation.
