Description
Null pointer dereference in Windows LDAP - Lightweight Directory Access Protocol allows an unauthorized attacker to deny service over a network.
Published: 2026-02-10
Score: 7.5 High
EPSS: < 1% Very Low
KEV: No
Impact: Denial of Service
Action: Patch
AI Analysis

Impact

A null pointer dereference in the Windows Lightweight Directory Access Protocol (LDAP) component allows an unauthorized attacker to trigger a service crash that renders the LDAP service unavailable. The flaw arises from improper handling of a null pointer and can be exploited by sending specially crafted LDAP requests.

Affected Systems

Microsoft Windows Server 2019, Windows Server 2019 Server Core, Windows Server 2022, Windows Server 2022 Server Core, Windows Server 2022 23H2, Windows Server 2025, and Windows Server 2025 Server Core installations are affected.

Risk and Exploitability

The CVSS score of 7.5 indicates high severity, but the EPSS score of less than 1% shows a low but nonzero likelihood of exploitation. The vulnerability is not listed in the CISA KEV catalog. Exploitation is inferred to occur remotely over the network by an unauthorized actor issuing crafted LDAP requests, which would cause the LDAP service to crash and deny availability to legitimate users.

Generated by OpenCVE AI on April 15, 2026 at 17:22 UTC.

Remediation

No vendor fix or workaround currently provided.

OpenCVE Recommended Actions

  • Apply any Microsoft security update that addresses CVE-2026-21243
  • Restart the Windows LDAP service to ensure the patch takes effect
  • Restrict LDAP traffic to trusted IP ranges using firewall rules

Generated by OpenCVE AI on April 15, 2026 at 17:22 UTC.

Tracking

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Advisories

No advisories yet.

History

Thu, 12 Feb 2026 12:30:00 +0000

Type Values Removed Values Added
First Time appeared Microsoft windows Server 2019 (server Core Installation)
Microsoft windows Server 2022, 23h2 Edition (server Core Installation)
Microsoft windows Server 2025 (server Core Installation)
Vendors & Products Microsoft windows Server 2019 (server Core Installation)
Microsoft windows Server 2022, 23h2 Edition (server Core Installation)
Microsoft windows Server 2025 (server Core Installation)

Wed, 11 Feb 2026 20:45:00 +0000

Type Values Removed Values Added
First Time appeared Microsoft windows Server 2022 23h2
CPEs cpe:2.3:o:microsoft:windows_server_2022_23h2:*:*:*:*:*:*:*:*
Vendors & Products Microsoft windows Server 2022 23h2

Wed, 11 Feb 2026 16:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Tue, 10 Feb 2026 18:15:00 +0000

Type Values Removed Values Added
Description Null pointer dereference in Windows LDAP - Lightweight Directory Access Protocol allows an unauthorized attacker to deny service over a network.
Title Windows Lightweight Directory Access Protocol (LDAP) Denial of Service Vulnerability
First Time appeared Microsoft
Microsoft windows Server 2019
Microsoft windows Server 2022
Microsoft windows Server 2025
Microsoft windows Server 23h2
Weaknesses CWE-476
CPEs cpe:2.3:o:microsoft:windows_server_2019:*:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2022:*:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2025:*:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_23h2:*:*:*:*:*:*:*:*
Vendors & Products Microsoft
Microsoft windows Server 2019
Microsoft windows Server 2022
Microsoft windows Server 2025
Microsoft windows Server 23h2
References
Metrics cvssV3_1

{'score': 7.5, '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'}

Subscriptions

Microsoft Windows Server 2019 Windows Server 2019 (server Core Installation) Windows Server 2022 Windows Server 2022, 23h2 Edition (server Core Installation) Windows Server 2022 23h2 Windows Server 2025 Windows Server 2025 (server Core Installation) Windows Server 23h2
cve-icon MITRE

Status: PUBLISHED

Assigner: microsoft

Published:

Updated: 2026-04-10T13:21:29.930Z

Reserved: 2025-12-11T21:02:05.735Z

Link: CVE-2026-21243

cve-icon Vulnrichment

Updated: 2026-02-11T15:27:54.095Z

cve-icon NVD

Status : Analyzed

Published: 2026-02-10T18:16:25.480

Modified: 2026-02-11T20:41:23.863

Link: CVE-2026-21243

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-04-15T17:45:10Z

Weaknesses