CVE-2026-21243 json
Windows Lightweight Directory Access Protocol (LDAP) Denial of Service Vulnerability
published 8mo ago modified 2mo 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
Is CVE-2026-21243 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.
Check with FencerCISA SSVC
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
- Assessed
- 8mo ago
Exploit prediction
1.41% chance of exploitation in the next 30 days, higher than 72% of all scored CVEs (FIRST EPSS, 2026-11-09).
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
-
- CWE-476 NULL Pointer Dereference
References
-
msrc.microsoft.com
/update-guide/vulnerability/CVE-2026-21243
vendor-advisory, patch
Sources
- CVE List CVE-2026-21243
- NVD CVE-2026-21243
Fencer Intel 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.