CVE-2026-21525

Windows Remote Access Connection Manager Denial of Service Vulnerability

CVSS 3.1 Medium 6.2Known exploited (CISA KEV)

CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C

Description

Null pointer dereference in Windows Remote Access Connection Manager allows an unauthorized attacker to deny service locally.

Key data

CVSS 3.1 Medium 6.2

Score published by microsoft in the CVE record.

CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C

Attack vector: Local
The attacker needs local access to the system, or to trick a user into running something.
Attack complexity: Low
No special conditions are needed. The attack can be repeated at will.
Privileges required: None
No account or privileges are needed.
User interaction: None
No action from any user is needed.
Scope: Unchanged
The impact stays within the vulnerable component.
Confidentiality impact: None
No effect on the secrecy of data.
Integrity impact: None
No effect on the trustworthiness of data.
Availability impact: High
Serious or total effect on availability.

Metric	Value	What it means
Attack vector	Local	The attacker needs local access to the system, or to trick a user into running something.
Attack complexity	Low	No special conditions are needed. The attack can be repeated at will.
Privileges required	None	No account or privileges are needed.
User interaction	None	No action from any user is needed.
Scope	Unchanged	The impact stays within the vulnerable component.
Confidentiality impact	None	No effect on the secrecy of data.
Integrity impact	None	No effect on the trustworthiness of data.
Availability impact	High	Serious or total effect on availability.

CVSS is owned and managed by FIRST.Org, Inc. (FIRST) and is used by permission. Each CVSS score on this site is shown together with its vector string, as published in the CVE record by the source named next to it. Learn more at first.org/cvss.

EPSS

Exploit Prediction Scoring System by FIRST: an estimate of the probability that exploitation activity will be observed in the next 30 days.

Score: 0.05041 (5.0% probability)
Percentile: 92.4%
Scores of: Nov 10, 2026
Model: v2026.06.15

CISA Known Exploited Vulnerabilities

This CVE is listed in the CISA KEV catalog.

Name in the catalog: Microsoft Windows NULL Pointer Dereference Vulnerability
Added to the catalog: Feb 10, 2026
Federal due date: Mar 3, 2026

CISA assessment as of Feb 11, 2026

Stakeholder-Specific Vulnerability Categorization (SSVC) decision points added by CISA.

Exploitation: Recorded by CISA as active
Automatable: no
Technical impact: partial

Weakness (CWE)

CWE catalog version 5.0.

CWE-476NULL Pointer Dereference

Affected products

Products listed in the CVE record, as the CNA published them.

Microsoft Windows 10 Version 1607
- affected: 10.0.14393.0 up to before 10.0.14393.8868
Microsoft Windows 10 Version 1809
- affected: 10.0.17763.0 up to before 10.0.17763.8389
Microsoft Windows 10 Version 21H2
- affected: 10.0.19044.0 up to before 10.0.19044.6937
Microsoft Windows 10 Version 22H2
- affected: 10.0.19045.0 up to before 10.0.19045.6937
Microsoft Windows 11 version 22H3
- affected: 10.0.22631.0 up to before 10.0.22631.6649
Microsoft Windows 11 Version 23H2
- affected: 10.0.22631.0 up to before 10.0.22631.6649
Microsoft Windows 11 Version 24H2
- affected: 10.0.26100.0 up to before 10.0.26100.7840
Microsoft Windows 11 Version 25H2
- affected: 10.0.26200.0 up to before 10.0.26200.7840
Microsoft Windows 11 version 26H1
- affected: 10.0.28000.0 up to before 10.0.28000.1575
Microsoft Windows 11 Version 26H1
- affected: 10.0.28000.0 up to before 10.0.28000.1575
Microsoft Windows Server 2012
- affected: 6.2.9200.0 up to before 6.2.9200.25923
Microsoft Windows Server 2012 (Server Core installation)
- affected: 6.2.9200.0 up to before 6.2.9200.25923
Microsoft Windows Server 2012 R2
- affected: 6.3.9600.0 up to before 6.3.9600.23022
Microsoft Windows Server 2012 R2 (Server Core installation)
- affected: 6.3.9600.0 up to before 6.3.9600.23022
Microsoft Windows Server 2016
- affected: 10.0.14393.0 up to before 10.0.14393.8868
Microsoft Windows Server 2016 (Server Core installation)
- affected: 10.0.14393.0 up to before 10.0.14393.8868
Microsoft Windows Server 2019
- affected: 10.0.17763.0 up to before 10.0.17763.8389
Microsoft Windows Server 2019 (Server Core installation)
- affected: 10.0.17763.0 up to before 10.0.17763.8389
Microsoft Windows Server 2022
- affected: 10.0.20348.0 up to before 10.0.20348.4773
Microsoft Windows Server 2022, 23H2 Edition (Server Core installation)
- affected: 10.0.25398.0 up to before 10.0.25398.2149
Microsoft Windows Server 2025
- affected: 10.0.26100.0 up to before 10.0.26100.32370
Microsoft Windows Server 2025 (Server Core installation)
- affected: 10.0.26100.0 up to before 10.0.26100.32370

References

Links listed in the CVE record. They lead to other sites, which CubePath does not control.

Windows Remote Access Connection Manager Denial of Service Vulnerability (msrc.microsoft.com)vendor-advisorypatch
vicarius.io/vsociety/posts/cve-2026-21525-detection-script-…
vicarius.io/vsociety/posts/cve-2026-21525-mitigation-script…

Timeline

ID reservedDec 30, 2025
Added to CISA KEVFeb 10, 2026
Record publishedFeb 10, 2026
Record last updatedAug 19, 2026

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Data from the CVE Program (MITRE), CISA KEV and FIRST EPSS. CVSS is owned by FIRST and used by permission. Not affiliated with or endorsed by MITRE, CISA or FIRST. Data as of Nov 10, 2026, 19:12 UTC. Sources and licenses