CVE-2026-21525 – Windows Remote Access Connection Manager Denial of Service Vulnerability

CVE-2026-21525 is a moderate-severity denial of service vulnerability affecting the Windows Remote Access Connection Manager. The flaw is caused by a null pointer dereference condition that allows an unauthorized local attacker to crash the affected service. While it does not expose data or allow code execution, it can disrupt network connectivity and availability on impacted systems. Microsoft has confirmed that exploitation has been detected.

CVSS Score: 6.2 SEVERITY: Moderate THREAT: Denial of Service

EXPLOITS: There are no publicly disclosed exploit tools or proof-of-concept code. However, Microsoft has confirmed that exploitation has been detected, indicating the vulnerability has been abused in real-world scenarios despite the lack of public exploit details.

TECHNICAL SUMMARY: The vulnerability occurs when Windows Remote Access Connection Manager processes certain requests and fails to properly handle a null pointer reference. This results in a system-level exception that causes the service to terminate unexpectedly. An attacker does not need authentication or user interaction to trigger the condition locally, leading to a denial of service affecting remote access and networking functionality.

EXPLOITABILITY: This issue affects supported Windows systems where the Remote Access Connection Manager service is enabled. Exploitation is local, requires no privileges, and does not rely on user interaction. An attacker with basic local access can repeatedly trigger the flaw to cause persistent service disruption.

BUSINESS IMPACT: Denial of service conditions on Windows systems can disrupt remote connectivity, VPN access, and dependent services. In enterprise environments, this may lead to operational downtime, loss of remote workforce productivity, and potential service outages. Repeated exploitation could be used as a distraction or to degrade system reliability during broader attack activity.

WORKAROUND: If the patch cannot be applied immediately, organizations should restrict unnecessary local access to systems, monitor service crashes related to remote access components, and ensure rapid service recovery procedures are in place to reduce downtime.