---
title: "CVE-2026-21525: Microsoft Windows NULL Pointer Dereference Vulnerability"
url: https://erroneo.us/security/cve/CVE-2026-21525/
description: "CVE-2026-21525 (Microsoft Windows): Exploited in the wild (CISA KEV). Null pointer dereference in Windows Remote Access Connection Manager allows an…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-02-10
date_modified: 2026-08-19
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-21525"
kev: true
cvss: 6.2
epss: 0.04825
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-21525: Microsoft Windows NULL Pointer Dereference Vulnerability

**Signal:** Exploited: patch now if you run it. CISA has confirmed exploitation in the wild. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Yes, if you run Microsoft Windows. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2026-02-10, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2026-03-03 ; treat that as the outer limit, not the target.
- EPSS 4.8% , percentile 92: FIRST’s model estimates a 4.8% chance of exploitation activity in the next 30 days, higher than 92% of all scored CVEs (elevated). EPSS is a probability, not a verdict.
- Needs local access needed. Lower urgency for most teams unless an attacker could already run code on the machine.

## What it is

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

## Affected products (CVE record)

- Microsoft Windows 10 Version 1607: 10.0.14393.0 < 10.0.14393.8868
- Microsoft Windows 10 Version 1809: 10.0.17763.0 < 10.0.17763.8389
- Microsoft Windows 10 Version 21H2: 10.0.19044.0 < 10.0.19044.6937
- Microsoft Windows 10 Version 22H2: 10.0.19045.0 < 10.0.19045.6937
- Microsoft Windows 11 version 22H3: 10.0.22631.0 < 10.0.22631.6649
- Microsoft Windows 11 Version 23H2: 10.0.22631.0 < 10.0.22631.6649
- Microsoft Windows 11 Version 24H2: 10.0.26100.0 < 10.0.26100.7840
- Microsoft Windows 11 Version 25H2: 10.0.26200.0 < 10.0.26200.7840
- Microsoft Windows 11 version 26H1: 10.0.28000.0 < 10.0.28000.1575
- Microsoft Windows 11 Version 26H1: 10.0.28000.0 < 10.0.28000.1575

## Severity

- microsoft CVSS 3.1: 6.2 `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`

## Exploitation

- CISA KEV: added 2026-02-10; federal due date 2026-03-03. Known ransomware use: Unknown.
- CISA 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.
- CISA SSVC assessment: exploitation active , automatable no , technical impact partial .
- FIRST EPSS (model of 2026-10-21): 4.83% probability of exploitation activity in the next 30 days; percentile 92.

## Sources

- [Windows Remote Access Connection Manager Denial of Service Vulnerability](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21525)
- [CVE.org record CVE-2026-21525](https://www.cve.org/CVERecord?id=CVE-2026-21525)
- [NVD entry CVE-2026-21525](https://nvd.nist.gov/vuln/detail/CVE-2026-21525)
- [CISA Known Exploited Vulnerabilities catalog entry](https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-21525)
- [vicarius.io](https://www.vicarius.io/vsociety/posts/cve-2026-21525-detection-script-dos-vulnerability-in-windows-remote-access-connection-manager)
- [vicarius.io](https://www.vicarius.io/vsociety/posts/cve-2026-21525-mitigation-script-dos-vulnerability-in-windows-remote-access-connection-manager)

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Source page: https://erroneo.us/security/cve/CVE-2026-21525/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt