CVE-2026-21525: Microsoft Windows NULL Pointer Dereference Vulnerability

This vulnerability is a null pointer dereference in the Remote Access Connection Manager component of Microsoft Windows. An unauthorized attacker with local access can trigger it to crash the service and deny availability. It matters for Windows environments that rely on this component for remote access functions, as the issue requires no network access and can be triggered locally.

How it works

The weakness is classified under CWE-476. In this class of flaw, program code attempts to read or write through a pointer variable whose value is null because initialization or error checking failed earlier in execution.

An attacker with local access supplies input or environmental conditions that cause the Remote Access Connection Manager to reach the defective code path, dereference the null pointer, and terminate the process.

Am I affected? How to find it in your systems

The affected component runs on Microsoft Windows systems where remote access features are present or enabled. Begin inventory by enumerating Windows endpoints and servers, then inspect running services for Remote Access Connection Manager.

• Review service configuration and startup settings on each system.
• Check Windows Event Logs for repeated unexpected terminations of the associated process.
• Confirm exact versions and configurations against the vendor advisory, as public detail is limited.

How to remediate

Apply the vendor update named in the advisory as the primary step. After patching, review dependent services and configurations that interact with Remote Access Connection Manager.

• Follow applicable BOD 22-01 guidance for any cloud-hosted instances.
• Disable the component if it is not required for operations.

If you can't patch immediately

Limit local execution opportunities through endpoint controls and user privilege restrictions. Monitor Windows Event Logs and service health metrics for sudden crashes that match the affected component.

• Apply network segmentation to reduce the number of systems reachable by local attackers.
• Consider virtual patching or application control policies that block execution of unpatched binaries where feasible.
• Discontinue use of the product if mitigations cannot be applied.

If your data may have been exposed

Denial-of-service conditions from exploited vulnerabilities can form part of broader attack sequences that result in data exposure. You can run a free exposure scan of your email addresses to check against known breach data.