CVE-2026-21243: Windows Lightweight Directory Access Protocol (LDAP) Denial of Service Vulnerability

Overview

Severity

High (CVSS 7.5)

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C

Category

Denial of Service

Exploit Status

Not Exploited

Exploitation Likelihood

Unlikely

Patch Tuesday

2026-Feb

Released

2026-02-10

EPSS Score

0.09% (percentile: 24.9%)

Description

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

Affected Products (7)

Windows

• Windows Server 2019
• Windows Server 2019 (Server Core installation)
• Windows Server 2022
• Windows Server 2022 (Server Core installation)
• Windows Server 2025 (Server Core installation)
• Windows Server 2022, 23H2 Edition (Server Core installation)
• Windows Server 2025

Security Updates (6)

• 5075904
• 5075906
• 5075943
• 5075899
• 5075942
• 5075897

Acknowledgments

MORSE (Microsoft Offensive Research and Security Engineering)

Revision History

• 2026-02-10: Information published.