High MSRC-CVE-2026-21243 1 CVE

Windows Lightweight Directory Access Protocol (LDAP) Denial of Service Vulnerability

Published Feb 10, 2026 · Updated Feb 10, 2026

Vendor: Microsoft

Summary

Impact: Denial of Service. Microsoft rating: Important. Not known to be exploited — Exploitation Unlikely. Customer action: Required.

Details

Security updates
10.0.17763.8389 — https://support.microsoft.com/help/5075904
10.0.20348.4773 — https://support.microsoft.com/help/5075906
10.0.20348.4711 — https://support.microsoft.com/help/5075943
10.0.26100.32370 — https://support.microsoft.com/help/5075899
10.0.26100.32313 — https://support.microsoft.com/help/5075942
10.0.25398.2149 — https://support.microsoft.com/help/5075897

Vulnerabilities 1

High 7.5

CVE-2026-21243

Windows Lightweight Directory Access Protocol (LDAP) Denial of Service Vulnerability

Null pointer dereference in Windows LDAP - Lightweight Directory Access Protocol allows an unauthorized attacker to deny service over a network.

Microsoft Windows Server 2019 Windows Server 2019 (Server Core installation) Windows Server 2022 Windows

Feb 10, 2026

Revision history

2026-02-10 #1
Information published.

References

CVE-2026-21243 Windows Lightweight Directory Access Protocol (LDAP) Denial of Service Vulnerability - HTML
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21243
Microsoft Exploitability Index
https://www.microsoft.com/en-us/msrc/exploitability-index?rtc=1
Microsoft Support Lifecycle
https://support.microsoft.com/lifecycle
Common Vulnerability Scoring System
https://www.first.org/cvss