What is CVE-2026-21243?

CVE-2026-21243 is a security advisory published by Microsoft with High severity. EchelonGraph links Microsoft's advisory rather than copying its page; it is at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21243.

Which CVE IDs does CVE-2026-21243 cover?

CVE-2026-21243 covers the following CVE IDs: CVE-2026-21243. Each CVE has its own detail page on EchelonGraph Pulse with its EchelonGraph score.

What is the CVSS v3 score of CVE-2026-21243?

CVE-2026-21243 has a CVSS v3 base score of 7.5, published by Microsoft Security Response Center (MSRC).

Which products are affected by CVE-2026-21243?

CVE-2026-21243 affects 7 products, including: Windows Server 2019; Windows Server 2019 (Server Core installation); Windows Server 2022; Windows Server 2022 (Server Core installation); Windows Server 2022, 23H2 Edition (Server Core installation); and others — see the full list on the advisory page.

How do I remediate CVE-2026-21243?

Microsoft lists 6 KB articles for CVE-2026-21243: KB5075904, KB5075906, KB5075943, KB5075899, KB5075942, KB5075897. Each is listed on this page with its fixed build; Microsoft's advisory is at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21243.

CVE-2026-21243HighMicrosoft CVSS 7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C

Microsoft security update for CVE-2026-21243 — Windows Server

Vendor

Microsoft Security Response Center (MSRC)

Published

February 10, 2026

Last Modified

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🔗 CVE IDs covered (1)

CVE-2026-21243 →

📋 Microsoft's advisory

EchelonGraph does not copy Microsoft's advisory page: its FAQ and remediation text are not shown here. Read the advisory on https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21243. This page also shows what EchelonGraph holds for CVE-2026-21243, with the description from its CVE record, which the CVE Numbering Authority that assigned the CVE wrote: for a CVE Microsoft assigned, often in the words of Microsoft's own advisory.

🎯 Affected products7

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

✅ Updates Microsoft lists: 6 KB articles

6 rows: one per KB article or update, update type and fixed build. Their details are on Microsoft's advisory.

KB article	Update	Fixed build
KB5075904	Security Update	10.0.17763.8389
KB5075906	Security Update	10.0.20348.4773
KB5075943	Security Hotpatch Update	10.0.20348.4711
KB5075899	Security Update	10.0.26100.32370
KB5075942	Security Hotpatch Update	10.0.26100.32313
KB5075897	Security Update	10.0.25398.2149

🧭 EchelonGraph on CVE-2026-21243

EchelonGraph score: 7.5 HIGH
CISA KEV: Not listed
Fix status: A fix is available — apply it.

Description from the CVE record (CVE.org), as published by its numbering authority

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

Published by Microsoft Corporation, the CVE Numbering Authority that assigned CVE-2026-21243, in its CVE record at CVE.org; reused under the CVE Program's Terms of Use (its licence and MITRE's copyright notice are in our Terms of Service).

🔗 CVE IDs covered (1)

📋 Microsoft's advisory

🎯 Affected products7

✅ Updates Microsoft lists: 6 KB articles

🧭 EchelonGraph on CVE-2026-21243

🔗 References (13)