CVEs / CVE-2026-21525
CVE-2026-21525: Microsoft Windows NULL Pointer Dereference Vulnerability
- Known exploited in the CISA KEV catalog since 10 Feb 2026
- medium 6.2 CVSS 3.1 (from the CNA)
- EPSS 4.86% chance of exploitation in the next 30 days, higher than 92% of CVEs (30 Oct 2026)
- Last changed at its sources
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Summary
Microsoft Windows Remote Access Connection Manager contains a NULL pointer dereference that could allow an unauthorized attacker to deny service locally.
Description
Null pointer dereference in Windows Remote Access Connection Manager allows an unauthorized attacker to deny service locally.
Affected and fixed versions
| Product | Affected | Fixed in |
|---|---|---|
| Microsoft Windows 10 Version 1607 | from 10.0.14393.0, before 10.0.14393.8868 | 10.0.14393.8868 |
| Microsoft Windows 10 Version 1809 | from 10.0.17763.0, before 10.0.17763.8389 | 10.0.17763.8389 |
| Microsoft Windows 10 Version 21H2 | from 10.0.19044.0, before 10.0.19044.6937 | 10.0.19044.6937 |
| Microsoft Windows 10 Version 22H2 | from 10.0.19045.0, before 10.0.19045.6937 | 10.0.19045.6937 |
| Microsoft Windows 11 version 22H3 | from 10.0.22631.0, before 10.0.22631.6649 | 10.0.22631.6649 |
| Microsoft Windows 11 Version 23H2 | from 10.0.22631.0, before 10.0.22631.6649 | 10.0.22631.6649 |
| Microsoft Windows 11 Version 24H2 | from 10.0.26100.0, before 10.0.26100.7840 | 10.0.26100.7840 |
| Microsoft Windows 11 Version 25H2 | from 10.0.26200.0, before 10.0.26200.7840 | 10.0.26200.7840 |
| Microsoft Windows 11 version 26H1 | from 10.0.28000.0, before 10.0.28000.1575 | 10.0.28000.1575 |
| Microsoft Windows 11 Version 26H1 | from 10.0.28000.0, before 10.0.28000.1575 | 10.0.28000.1575 |
| Microsoft Windows Server 2012 | from 6.2.9200.0, before 6.2.9200.25923 | 6.2.9200.25923 |
| Microsoft Windows Server 2012 (Server Core installation) | from 6.2.9200.0, before 6.2.9200.25923 | 6.2.9200.25923 |
| Microsoft Windows Server 2012 R2 | from 6.3.9600.0, before 6.3.9600.23022 | 6.3.9600.23022 |
| Microsoft Windows Server 2012 R2 (Server Core installation) | from 6.3.9600.0, before 6.3.9600.23022 | 6.3.9600.23022 |
| Microsoft Windows Server 2016 | from 10.0.14393.0, before 10.0.14393.8868 | 10.0.14393.8868 |
| Microsoft Windows Server 2016 (Server Core installation) | from 10.0.14393.0, before 10.0.14393.8868 | 10.0.14393.8868 |
| Microsoft Windows Server 2019 | from 10.0.17763.0, before 10.0.17763.8389 | 10.0.17763.8389 |
| Microsoft Windows Server 2019 (Server Core installation) | from 10.0.17763.0, before 10.0.17763.8389 | 10.0.17763.8389 |
| Microsoft Windows Server 2022 | from 10.0.20348.0, before 10.0.20348.4773 | 10.0.20348.4773 |
| Microsoft Windows Server 2022, 23H2 Edition (Server Core installation) | from 10.0.25398.0, before 10.0.25398.2149 | 10.0.25398.2149 |
| Microsoft Windows Server 2025 | from 10.0.26100.0, before 10.0.26100.32370 | 10.0.26100.32370 |
| Microsoft Windows Server 2025 (Server Core installation) | from 10.0.26100.0, before 10.0.26100.32370 | 10.0.26100.32370 |
Exploitation
| In CISA KEV since | 10 Feb 2026 |
|---|---|
| Due date for US federal agencies | 3 Mar 2026 |
| Used in ransomware campaigns | Unknown |
| Required action | Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. |
Severity
| CVSS 3.1 | 6.2 mediumCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HScored by the CNA ([email protected]) |
|---|---|
| Weakness | CWE-476 |
References
- CVE-2026-21525 on NVD
- CVE-2026-21525 in the CISA KEV catalog
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21525 (cited by CISA)
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21525 Vendor Advisory
- https://www.vicarius.io/vsociety/posts/cve-2026-21525-detection-script-dos-vulnerability-in-windows-remote-access-connection-manager Third Party Advisory
- https://www.vicarius.io/vsociety/posts/cve-2026-21525-mitigation-script-dos-vulnerability-in-windows-remote-access-connection-manager Mitigation, Third Party Advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-21525 US Government Resource
Sources
Exploitation status from the CISA Known Exploited Vulnerabilities catalog. EPSS scores from FIRST. Descriptions, severity and references from the National Vulnerability Database. Open-source package versions from OSV (CC-BY 4.0). Text is shown as each source states it; Stackurity does not edit it. Check the vendor's advisory before acting.
This product uses data from the NVD API but is not endorsed or certified by the NVD.