CVE-2026-50656: Microsoft Defender Elevation of Privilege Vulnerability

Synopsis

This is an elevation of privilege vulnerability in the Microsoft Malware Protection Engine, the core scanning component of Microsoft Defender. An attacker who already has a low-privilege account on the affected host can exploit this locally, without any network access or user interaction, to gain full control over the system. Successful exploitation gives the attacker high-level read, write, and execution capabilities across the host. No fix version has been published yet; HarborGuard tracks this advisory and will flag a patched-image rebuild the moment Microsoft ships a security update.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityNot required

  The attacker needs an existing shell or process on the host; no network access to the target is required.

• AuthenticationRequired

  Any low-privilege local account is sufficient; no administrative or elevated credentials are needed to begin the attack.

• Victim interactionNot required

  The exploit executes without any action from another user on the system.

• Attack complexityDetail

  The exploit is reliable and requires no special race conditions or environmental configuration; it succeeds consistently given local access.

Blast Radius

• A successful attacker reads any file on the host, including credential stores, secrets, and application data.
• A successful attacker writes or modifies any file on the host, including system binaries and security tool configurations.
• A successful attacker crashes or terminates any process, including the Defender engine itself, removing malware detection from the host.
• Combined read, write, and availability control means the attacker can effectively own the host, pivot to adjacent systems, or establish persistence.