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

Executive Summary

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

Overview

7.5

CVSS HIGH

Important

MS Severity

Not Exploited

MS Exploit Status

Exploitation Unlikely

MS Exploit Likelihood

Category Denial of Service

Weakness CWE-476: NULL Pointer Dereference

Released Feb 10 2026

Last Updated Feb 10 2026

Publicly Disclosed No

CISA KEV Not Listed

Known Exploits None Known

EPSS Score 0.0134 — 0.68366 percentile

NVD CVSS 7.5 HIGH — matches MSRC

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

ATTACK VECTOR

Network

ATTACK COMPLEXITY

Low

PRIVILEGES REQUIRED

None

USER INTERACTION

None

SCOPE

Unchanged

CONFIDENTIALITY

None

INTEGRITY

None

AVAILABILITY

High

EXPLOIT CODE MATURITY

Unproven

REMEDIATION LEVEL

Official Fix

REPORT CONFIDENCE

Confirmed

Temporal Score: 6.5

EPSS Score

0.0134

probability of exploitation in the next 30 days

0.68366 percentile - updated 2026-07-25

View on FIRST.org

Affected Products

3 affected products

Product	KB Article	Severity	Impact	Restart Required
Windows Server 2019	`5075904 (Security Update)`	Important	Denial of Service	Yes
Windows Server 2019 (Server Core installation)	`5075904 (Security Update)`	Important	Denial of Service	Yes
Windows Server 2022 5075906 (Security Update) 5075943 (Security Hotpatch Update) Important Denial of Service 5073457 Base: 7.5 Temporal: 6.5 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 10.0.20348.4773 10.0.20348.4711 Yes None Windows Server 2022 (Server Core installation) 5075906 (Security Update) 5075943 (Security Hotpatch Update) Important Denial of Service 5073457 Base: 7.5 Temporal: 6.5 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 10.0.20348.4773 10.0.20348.4711 Yes None Windows Server 2022, 23H2 Edition (Server Core installation)	`5075897 (Security Update)`	Important	Denial of Service	Yes

Patches

2 patches

Article	Type	Restart
`5075904`	Security Update	Yes
`5075897`	Security Update	Yes

Known Exploits

No known exploits have been linked for this CVE yet. When available, exploit references will be sourced from public repositories and may be unverified, incomplete, or non-functional. Always review code carefully before use in any environment.

Acknowledgments

MORSE (Microsoft Offensive Research and Security Engineering)

References

MSRC Advisory MITRE NVD