---
id: "CVE-2026-21510"
kind: "vulnerability"
aliases: ["CVE-2026-21510"]
title: "Protection mechanism failure in Windows Shell allows an unauthorized attacker to bypass a security feature over a\u2026"
severity: "high"
cvss: 8.8
epss: null
exploited: true
status: "open"
category: "other"
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", "other", "windows"]
not_affected_if: ["unknown"]
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-2026-21510", "first_seen_at": "2026-10-23T19:11:51+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-21510", "first_seen_at": "2026-10-23T23:44:51+00:00"}]
---

# Protection mechanism failure in Windows Shell allows an unauthorized attacker to bypass a security feature over a…

A protection mechanism failure in the Microsoft Windows Shell lets an unauthorized attacker bypass a security feature over the network. CISA lists it as actively exploited in the wild.

_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 mitigations per Microsoft's vendor instructions, as CISA requires; the sources do not name a patched build.

## Timeline

- 2026-10-23T19:11:51+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2026-21510
- 2026-10-23T23:44:51+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-21510

## From the sources

Microsoft Windows Shell contains a protection mechanism failure vulnerability that could allow an unauthorized attacker to bypass a security feature over a network.

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_