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Fencer Vulns
high 7.5

CVE-2026-21243 json

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

published 2026-02-10 8 mo ago modified 2026-08-19 2 mo ago also EUVD-2026-7317

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.4%
EPSS 1.4% chance of exploitation in 30 days, percentile 72%
public exploits
0
none known

Summary

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

Patch / fix

  • Microsoft Windows Server 2019 10.0.17763.8389
  • Microsoft Windows Server 2019 (Server Core installation) 10.0.17763.8389
  • Microsoft Windows Server 2022 10.0.20348.4773
  • Microsoft Windows Server 2022, 23H2 Edition (Server Core installation) 10.0.25398.2149
  • Microsoft Windows Server 2025 10.0.26100.32370
  • Microsoft Windows Server 2025 (Server Core installation) 10.0.26100.32370

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
8 mo ago

Exploit prediction

1.41% chance of exploitation in the next 30 days, higher than 72% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.5 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
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

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

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.