CVE-2026-21533 — Windows 10 21h2
HIGHCVE-2026-21533 is a high-severity (CVSS 7.8) Improper Privilege Management vulnerability in microsoft windows 10 21h2. It is in CISA's Known Exploited Vulnerabilities catalog (added 2026-02-10) — treat it as actively exploited and patch now. A fix is available — see the affected versions and patch details below.
Improper privilege management in Windows Remote Desktop allows an authorized attacker to elevate privileges locally.
Exploitation Status
Actively exploited in the wild
- Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2026-02-10. Federal agencies were required to remediate by 2026-03-03.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2026-21533.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-21533 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 394,415 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Description
Improper privilege management in Windows Remote Desktop allows an authorized attacker to elevate privileges locally.
Affected Products
windows 10 21h2microsoftwindows 10 22h2microsoftwindows 10 1607microsoftwindows 10 1809microsoftwindows 11 23h2microsoftwindows 11 24h2microsoftDetection & mitigation playbook
Vendor / applianceDetect
Inventory every microsoft windows 10 21h2 deployment and check each version against the affected-products list above.
Fix
Apply the microsoft windows 10 21h2 security patch or hotfix for CVE-2026-21533 on the affected version, following the vendor advisory for your exact build.
Workarounds
Close the privilege gap rather than the entry point: audit which accounts, roles and service identities can reach the affected operation, drop the component to the least privilege it actually needs, and review file and directory permissions created by earlier installs — a default left in place is what makes this reachable. Alongside that, restrict the management interface to trusted networks and apply the vendor's recommended configuration mitigations.
Frequently Asked Questions
Is CVE-2026-21533 being exploited in your environment?
Detect and block the exploit chain at execution, on systems you cannot patch yet.