---
id: "CVE-2026-21525"
kind: "vulnerability"
aliases: ["CVE-2026-21525"]
title: "Null pointer dereference in Windows Remote Access Connection Manager allows an unauthorized attacker to deny service\u2026"
severity: "medium"
cvss: 6.2
epss: null
exploited: true
status: "open"
category: "infrastructure"
products: [{"name": "Microsoft Windows", "fixed": [], "affected": "", "ecosystem": "vendor"}, {"name": "microsoft windows 10 1607", "fixed": ["10.0.14393.8868"], "affected": "< 10.0.14393.8868", "ecosystem": "vendor"}, {"name": "microsoft windows 10 1809", "fixed": ["10.0.17763.8389"], "affected": "< 10.0.17763.8389", "ecosystem": "vendor"}, {"name": "microsoft windows 10 21h2", "fixed": ["10.0.19044.6937"], "affected": "< 10.0.19044.6937", "ecosystem": "vendor"}, {"name": "microsoft windows 10 22h2", "fixed": ["10.0.19045.6937"], "affected": "< 10.0.19045.6937", "ecosystem": "vendor"}, {"name": "microsoft windows 11 23h2", "fixed": ["10.0.22631.6649"], "affected": "< 10.0.22631.6649", "ecosystem": "vendor"}, {"name": "microsoft windows 11 24h2", "fixed": ["10.0.26100.7781"], "affected": "< 10.0.26100.7781", "ecosystem": "vendor"}, {"name": "microsoft windows 11 25h2", "fixed": ["10.0.26200.7781"], "affected": "< 10.0.26200.7781", "ecosystem": "vendor"}, {"name": "microsoft windows server 2012", "fixed": [], "affected": "", "ecosystem": "vendor"}, {"name": "microsoft windows server 2012", "fixed": [], "affected": "= r2", "ecosystem": "vendor"}, {"name": "microsoft windows server 2016", "fixed": ["10.0.14393.8868"], "affected": "< 10.0.14393.8868", "ecosystem": "vendor"}, {"name": "microsoft windows server 2019", "fixed": ["10.0.17763.8389"], "affected": "< 10.0.17763.8389", "ecosystem": "vendor"}, {"name": "microsoft windows server 2022", "fixed": ["10.0.20348.4711"], "affected": "< 10.0.20348.4711", "ecosystem": "vendor"}, {"name": "microsoft windows server 2022 23h2", "fixed": ["10.0.25398.2149"], "affected": "< 10.0.25398.2149", "ecosystem": "vendor"}, {"name": "microsoft windows server 2025", "fixed": ["10.0.26100.32313"], "affected": "< 10.0.26100.32313", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["exploited", "infrastructure", "remote-access", "vpn", "windows"]
not_affected_if: ["no-remote-access-service-in-use"]
published_at: "2026-02-10T00:00:00+00:00"
first_seen_at: "2026-10-23T19:11:51+00:00"
updated_at: "2026-10-23T23:44:51+00:00"
sources: [{"source": "kev", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2026-21525", "first_seen_at": "2026-10-23T19:11:51+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-21525", "first_seen_at": "2026-10-23T23:44:51+00:00"}]
---

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

A NULL pointer dereference in the Windows Remote Access Connection Manager service lets an unauthorized attacker crash it and deny service on the local machine. CISA lists it as actively exploited, and the sources do not describe any code execution.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:Microsoft Windows affected ? fixed ?
- vendor:microsoft windows 10 1607 affected < 10.0.14393.8868 fixed 10.0.14393.8868
- vendor:microsoft windows 10 1809 affected < 10.0.17763.8389 fixed 10.0.17763.8389
- vendor:microsoft windows 10 21h2 affected < 10.0.19044.6937 fixed 10.0.19044.6937
- vendor:microsoft windows 10 22h2 affected < 10.0.19045.6937 fixed 10.0.19045.6937
- vendor:microsoft windows 11 23h2 affected < 10.0.22631.6649 fixed 10.0.22631.6649
- vendor:microsoft windows 11 24h2 affected < 10.0.26100.7781 fixed 10.0.26100.7781
- vendor:microsoft windows 11 25h2 affected < 10.0.26200.7781 fixed 10.0.26200.7781
- vendor:microsoft windows server 2012 affected ? fixed ?
- vendor:microsoft windows server 2012 affected = r2 fixed ?
- vendor:microsoft windows server 2016 affected < 10.0.14393.8868 fixed 10.0.14393.8868
- vendor:microsoft windows server 2019 affected < 10.0.17763.8389 fixed 10.0.17763.8389
- vendor:microsoft windows server 2022 affected < 10.0.20348.4711 fixed 10.0.20348.4711
- vendor:microsoft windows server 2022 23h2 affected < 10.0.25398.2149 fixed 10.0.25398.2149
- vendor:microsoft windows server 2025 affected < 10.0.26100.32313 fixed 10.0.26100.32313

## Fix

Apply the Microsoft security update for CVE-2026-21525 per vendor instructions; the sources do not name the patch or build.
If no mitigation is available, CISA says to discontinue use of the affected product.

## Timeline

- 2026-10-23T19:11:51+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2026-21525
- 2026-10-23T23:44:51+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-21525

## From the sources

Microsoft Windows Remote Access Connection Manager contains a NULL pointer dereference that could allow an unauthorized attacker to deny service locally.

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.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_