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CVE-2025-21218: Windows Kerberos Denial of Service Vulnerability

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 2.6% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-01-14 · updated 2026-06-17
• Weakness: CWE-400

Description

Windows Kerberos Denial of Service Vulnerability

Affected products

• Microsoft Windows Server 2012: r2
• Microsoft Windows Server 2016: before 10.0.14393.7699 — fixed in 10.0.14393.7699
• Microsoft Windows Server 2019: before 10.0.17763.6775 — fixed in 10.0.17763.6775
• Microsoft Windows Server 2022: before 10.0.20348.3091 — fixed in 10.0.20348.3091
• Microsoft Windows Server 2022, 23H2 Edition (Server Core installation): before 10.0.25398.1369 — fixed in 10.0.25398.1369
• Microsoft Windows Server 2025: before 10.0.26100.2894 — fixed in 10.0.26100.2894
• Microsoft Windows Server 2012: from 6.2.9200.0 before 6.2.9200.25273 — fixed in 6.2.9200.25273
• Microsoft Windows Server 2012 R2: from 6.3.9600.0 before 6.3.9600.22371 — fixed in 6.3.9600.22371
• Microsoft Windows Server 2016: from 10.0.14393.0 before 10.0.14393.7699 — fixed in 10.0.14393.7699
• Microsoft Windows Server 2019: from 10.0.17763.0 before 10.0.17763.6775 — fixed in 10.0.17763.6775
• Microsoft Windows Server 2022: from 10.0.20348.0 before 10.0.20348.3091 — fixed in 10.0.20348.3091
• Microsoft Windows Server 2022, 23H2 Edition (Server Core installation): from 10.0.25398.0 before 10.0.25398.1369 — fixed in 10.0.25398.1369
• Microsoft Windows Server 2025: from 10.0.26100.0 before 10.0.26100.2894 — fixed in 10.0.26100.2894

How to fix

Upgrade to a fixed version: Microsoft Windows Server 2016 10.0.14393.7699; Microsoft Windows Server 2019 10.0.17763.6775; Microsoft Windows Server 2022 10.0.20348.3091; Microsoft Windows Server 2022, 23H2 Edition (Server Core installation) 10.0.25398.1369; Microsoft Windows Server 2025 10.0.26100.2894; Microsoft Windows Server 2012 6.2.9200.25273; Microsoft Windows Server 2012 R2 6.3.9600.22371; Microsoft Windows Server 2016 10.0.14393.7699; Microsoft Windows Server 2019 10.0.17763.6775; Microsoft Windows Server 2022 10.0.20348.3091; Microsoft Windows Server 2022, 23H2 Edition (Server Core installation) 10.0.25398.1369; Microsoft Windows Server 2025 10.0.26100.2894. Check the vendor advisory for mitigations.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-21218

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