CVE-2026-21525
Published: 10 February 2026
Summary
CVE-2026-21525 is a medium-severity NULL Pointer Dereference (CWE-476) vulnerability in Microsoft Windows 10 21H2. Its CVSS base score is 6.2 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Application or System Exploitation (T1499.004); ranked in the top 8.9% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog.
The strongest mitigations our analysis identified are NIST 800-53 SI-2 (Flaw Remediation) and RA-5 (Vulnerability Monitoring and Scanning).
Deeper analysis
CVE-2026-21525 is a null pointer dereference vulnerability (CWE-476) in the Windows Remote Access Connection Manager service. Published on 2026-02-10, it carries a CVSS v3.1 base score of 6.2 (AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) and affects Windows systems running this component, enabling local denial of service.
An unauthorized attacker with local access to the target system can exploit the vulnerability with low attack complexity and no privileges or user interaction required. Exploitation triggers a null pointer dereference, resulting in a denial of service that causes high availability impact while leaving confidentiality and integrity unaffected.
Microsoft's update guide at msrc.microsoft.com provides patching details and advisories for remediation. Vicarius offers specific detection and mitigation scripts tailored to this DoS issue in the Remote Access Connection Manager. The vulnerability is also listed in CISA's Known Exploited Vulnerabilities catalog.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-7329
Vulnerability details
Null pointer dereference in Windows Remote Access Connection Manager allows an unauthorized attacker to deny service locally.
- CWE(s)
- KEV Date Added
- 10 February 2026
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
The vulnerability is a null pointer dereference in a Windows system service that enables local attackers to cause a denial of service via exploitation, directly mapping to Endpoint Denial of Service: Application or System Exploitation.
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Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly mandates timely flaw remediation through patching the null pointer dereference in Windows Remote Access Connection Manager as detailed in Microsoft's update guide.
Requires monitoring and implementing security advisories and directives from MSRC and CISA's Known Exploited Vulnerabilities catalog for this CVE.
Supports vulnerability scanning to identify and prioritize systems vulnerable to this local DoS in Remote Access Connection Manager.