Windows Remote Access Connection Manager Local DoS Vulnerability

Historical catalog analysis: CISA added this entry on February 10, 2026. The entry reflects catalog information retrieved on August 31, 2026, not a snapshot archived on the inclusion date. Check current vendor guidance before acting.

What the vulnerability is

CVE-2026-21525 is a NULL pointer dereference vulnerability (CWE-476) located within the Remote Access Connection Manager component of Microsoft Windows. This flaw could allow an unauthorized attacker with local access to trigger a denial of service (DoS) condition on the affected system.

Exposure and applicability

This vulnerability applies to environments running affected versions of Microsoft Windows. In healthcare settings, this is particularly relevant for workstations and servers that manage electronic Protected Health Information (ePHI) or support clinical workflows. Because the impact is a local denial of service, the primary risk involves an attacker who has already gained a foothold on the system or a malicious insider attempting to disrupt availability.

While a DoS event does not inherently imply data exfiltration, the loss of system availability can interrupt patient care continuity and hinder the ability of clinical staff to access critical health records in real-time, which is a core consideration for HIPAA Security Rule risk management regarding availability.

Remediation priorities

Our analysis suggests that healthcare organizations prioritize remediation based on the criticality of the affected asset to patient care. We recommend the following prioritized actions:

1. Apply Vendor Updates: The primary mitigation is to apply the security updates provided by Microsoft for this specific vulnerability. This should be prioritized for systems with high availability requirements.
2. Restrict Local Access: Since this is a local vulnerability, reducing the number of users and processes with local access to sensitive servers could reduce the likelihood of an unauthorized actor triggering the flaw.
3. Review System Availability Dependencies: Identify which clinical workflows depend on the Remote Access Connection Manager to ensure that a service disruption would not lead to an unacceptable impact on patient safety.

How to validate remediation

To verify that exposure has been reduced, security leaders and system administrators should:
* Verify Patch Application: Confirm through centralized patch management systems or Windows Update history that the specific update addressing CVE-2026-21525 has been successfully installed on all targeted endpoints.
* Configuration Audit: Review local account permissions to ensure the principle of least privilege is applied, limiting the potential for unauthorized local users to interact with vulnerable system components.

Limits and open questions

It remains unknown whether this vulnerability has been utilized in active ransomware campaigns. Additionally, while patching reduces the likelihood of this specific flaw being exploited, it does not eliminate all risks associated with local denial of service attacks or other vulnerabilities within the Windows ecosystem. Organizations should continue to coordinate any system changes with clinical engineering to ensure that updates do not interfere with specialized medical software or device integrations.

Source and editorial note

CVE-2026-21525: Microsoft Windows NULL Pointer Dereference Vulnerability · Source date: February 10, 2026 · Retrieved August 31, 2026.

Material facts are tied to the cited primary source. Recommendations are independent defensive analysis unless attributed to the source. Confirm consequential decisions against current authoritative guidance.

Archive date: February 13, 2026. The displayed post date is assigned three days after the source date to organize this retrospective archive; it does not mean this site published the analysis then. First published by this site: September 19, 2026 at 01:09 UTC.

Request a healthcare security assessment