CVE-2026-85319: Active Directory Federation Services (AD FS) Denial of Service Vulnerability

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-10-13 · updated 2026-10-31
Weakness: CWE-770

Description

Allocation of resources without limits or throttling in Active Directory Federation Services (AD FS) allows an unauthorized attacker to deny service over a network.

Affected products

Microsoft Windows 10 1607: before 10.0.14393.9612 — fixed in 10.0.14393.9612
Microsoft Windows 10: before 10.0.17763.9376 — fixed in 10.0.17763.9376
Microsoft Windows Server 2012: r2 (and their updates)
Microsoft Windows Server 2016: before 10.0.14393.9612 — fixed in 10.0.14393.9612
Microsoft Windows Server 2019: before 10.0.17763.9376 — fixed in 10.0.17763.9376
Microsoft Windows Server 2022: before 10.0.20348.5761 — fixed in 10.0.20348.5761
Microsoft Windows Server 2025: before 10.0.26100.33650 — fixed in 10.0.26100.33650
Microsoft Windows 10 1607: from 10.0.14393.0 before 10.0.14393.9612 — fixed in 10.0.14393.9612
Microsoft Windows 10: from 10.0.17763.0 before 10.0.17763.9376 — fixed in 10.0.17763.9376
Microsoft Windows Server 2012: from 6.2.9200.0 before 6.2.9200.26434 — fixed in 6.2.9200.26434
Microsoft Windows Server 2012 R2: from 6.3.9600.0 before 6.3.9600.23470 — fixed in 6.3.9600.23470
Microsoft Windows Server 2016: from 10.0.14393.0 before 10.0.14393.9612 — fixed in 10.0.14393.9612
Microsoft Windows Server 2019: from 10.0.17763.0 before 10.0.17763.9376 — fixed in 10.0.17763.9376
Microsoft Windows Server 2022: from 10.0.20348.0 before 10.0.20348.5761 — fixed in 10.0.20348.5761
Microsoft Windows Server 2025: from 10.0.26100.0 before 10.0.26100.33650 — fixed in 10.0.26100.33650

How to fix

Upgrade to a fixed version: Microsoft Windows 10 1607 10.0.14393.9612; Microsoft Windows 10 10.0.17763.9376; Microsoft Windows Server 2016 10.0.14393.9612; Microsoft Windows Server 2019 10.0.17763.9376; Microsoft Windows Server 2022 10.0.20348.5761; Microsoft Windows Server 2025 10.0.26100.33650; Microsoft Windows 10 1607 10.0.14393.9612; Microsoft Windows 10 10.0.17763.9376; Microsoft Windows Server 2012 6.2.9200.26434; Microsoft Windows Server 2012 R2 6.3.9600.23470; Microsoft Windows Server 2016 10.0.14393.9612; Microsoft Windows Server 2019 10.0.17763.9376. Check the vendor advisory for mitigations.

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-85319

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