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CVE-2026-21533: Microsoft Windows Improper Privilege Management Vulnerability

• Severity: high (CVSS 7.8 v3.1)
• Exploited in the wild: yes — in CISA KEV since 2026-02-10
• EPSS: 4.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-02-10 · updated 2026-06-17
• Weakness: CWE-269

Description

Improper privilege management in Windows Remote Desktop allows an authorized attacker to elevate privileges locally.

Affected products

• Microsoft Windows 10 1607: before 10.0.14393.8868 — fixed in 10.0.14393.8868
• Microsoft Windows 10: before 10.0.17763.8389 — fixed in 10.0.17763.8389
• Microsoft Windows 10: before 10.0.19044.6937 — fixed in 10.0.19044.6937
• Microsoft Windows 10: before 10.0.19045.6937 — fixed in 10.0.19045.6937
• Microsoft Windows 11: before 10.0.22631.6649 — fixed in 10.0.22631.6649
• Microsoft Windows 11: before 10.0.26100.7781 — fixed in 10.0.26100.7781
• Microsoft Windows 11 25H2: before 10.0.26200.7781 — fixed in 10.0.26200.7781
• Microsoft Windows Server 2012: r2
• Microsoft Windows Server 2016: before 10.0.14393.8868 — fixed in 10.0.14393.8868
• Microsoft Windows Server 2019: before 10.0.17763.8389 — fixed in 10.0.17763.8389
• Microsoft Windows Server 2022: before 10.0.20348.4711 — fixed in 10.0.20348.4711
• Microsoft Windows Server 2022, 23H2 Edition (Server Core installation): before 10.0.25398.2149 — fixed in 10.0.25398.2149
• Microsoft Windows Server 2025: before 10.0.26100.32313 — fixed in 10.0.26100.32313

How to fix

Upgrade to a fixed version: Microsoft Windows 10 1607 10.0.14393.8868; Microsoft Windows 10 10.0.17763.8389; Microsoft Windows 10 10.0.19044.6937; Microsoft Windows 10 10.0.19045.6937; Microsoft Windows 11 10.0.22631.6649; Microsoft Windows 11 10.0.26100.7781; Microsoft Windows 11 25H2 10.0.26200.7781; Microsoft Windows Server 2016 10.0.14393.8868; Microsoft Windows Server 2019 10.0.17763.8389; Microsoft Windows Server 2022 10.0.20348.4711; Microsoft Windows Server 2022, 23H2 Edition (Server Core installation) 10.0.25398.2149; Microsoft Windows Server 2025 10.0.26100.32313. Check the vendor advisory for mitigations.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21533
• https://www.vicarius.io/vsociety/posts/cve-2026-21533-detection-script-privilege-escalation-vulnerability-in-windows-remote-desktop
• https://www.vicarius.io/vsociety/posts/cve-2026-21533-mitigation-script-privilege-escalation-vulnerability-in-windows-remote-desktop
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-21533

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