Denial of service in Active Directory Federation Services (AD FS)
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-770.
Summary
Microsoft Active Directory Federation Services (AD FS) on Windows Server 2012 R2, 2016, 2019, 2022 and 2025 is affected. Allocation of resources without limits or throttling (CWE-770) lets an unauthorized remote attacker exhaust service resources and deny service. The attack needs no privileges or user interaction.
Written with Claude Haiku 5.5 from the sources below · 2026-10-28
Description from the CNA
Allocation of resources without limits or throttling in Active Directory Federation Services (AD FS) allows an unauthorized attacker to deny service over a network.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Microsoft | Windows Server 2012 R2 | 6.3.9600.0 to before 6.3.9600.23470 | 6.3.9600.23470 | Patch available | CNA |
| Microsoft | Windows Server 2012 R2 (Server Core installation) | 6.3.9600.0 to before 6.3.9600.23470 | 6.3.9600.23470 | Patch available | CNA |
| Microsoft | Windows Server 2016 | 10.0.14393.0 to before 10.0.14393.9612 | 10.0.14393.9612 | Patch available | CNA |
| Microsoft | Windows Server 2016 (Server Core installation) | 10.0.14393.0 to before 10.0.14393.9612 | 10.0.14393.9612 | Patch available | CNA |
| Microsoft | Windows Server 2019 | 10.0.17763.0 to before 10.0.17763.9376 | 10.0.17763.9376 | Patch available | CNA |
| Microsoft | Windows Server 2019 (Server Core installation) | 10.0.17763.0 to before 10.0.17763.9376 | 10.0.17763.9376 | Patch available | CNA |
| Microsoft | Windows Server 2022 | 10.0.20348.0 to before 10.0.20348.5761 | 10.0.20348.5761 | Patch available | CNA |
| Microsoft | Windows Server 2025 | 10.0.26100.0 to before 10.0.26100.33650 | 10.0.26100.33650 | Patch available | CNA |
| Microsoft | Windows Server 2025 (Server Core installation) | 10.0.26100.0 to before 10.0.26100.33650 | 10.0.26100.33650 | Patch available | CNA |
- Windows Server 2012 R2 VendorMicrosoft Affected 6.3.9600.0 to before 6.3.9600.23470 Fixed in 6.3.9600.23470 Patch available CNA
- Windows Server 2012 R2 (Server Core installation) VendorMicrosoft Affected 6.3.9600.0 to before 6.3.9600.23470 Fixed in 6.3.9600.23470 Patch available CNA
- Windows Server 2016 VendorMicrosoft Affected 10.0.14393.0 to before 10.0.14393.9612 Fixed in 10.0.14393.9612 Patch available CNA
- Windows Server 2016 (Server Core installation) VendorMicrosoft Affected 10.0.14393.0 to before 10.0.14393.9612 Fixed in 10.0.14393.9612 Patch available CNA
- Windows Server 2019 VendorMicrosoft Affected 10.0.17763.0 to before 10.0.17763.9376 Fixed in 10.0.17763.9376 Patch available CNA
- Windows Server 2019 (Server Core installation) VendorMicrosoft Affected 10.0.17763.0 to before 10.0.17763.9376 Fixed in 10.0.17763.9376 Patch available CNA
- Windows Server 2022 VendorMicrosoft Affected 10.0.20348.0 to before 10.0.20348.5761 Fixed in 10.0.20348.5761 Patch available CNA
- Windows Server 2025 VendorMicrosoft Affected 10.0.26100.0 to before 10.0.26100.33650 Fixed in 10.0.26100.33650 Patch available CNA
- Windows Server 2025 (Server Core installation) VendorMicrosoft Affected 10.0.26100.0 to before 10.0.26100.33650 Fixed in 10.0.26100.33650 Patch available CNA
CPE configurations NVD · 5
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:o:microsoft:windows_server_2012:r2:*:*:*:*:*:*:* | r2 | Vulnerable | Microsoft |
| cpe:2.3:o:microsoft:windows_server_2016:*:*:*:*:*:*:*:* | before 10.0.14393.9612 | Vulnerable | Microsoft |
| cpe:2.3:o:microsoft:windows_server_2019:*:*:*:*:*:*:*:* | before 10.0.17763.9376 | Vulnerable | Microsoft |
| cpe:2.3:o:microsoft:windows_server_2022:*:*:*:*:*:*:x64:* | before 10.0.20348.5761 | Vulnerable | Microsoft |
| cpe:2.3:o:microsoft:windows_server_2025:*:*:*:*:*:*:x64:* | before 10.0.26100.33650 | Vulnerable | Microsoft |
- cpe:2.3:o:microsoft:windows_server_2012:r2:*:*:*:*:*:*:* Versions r2 Vulnerable ·Microsoft
- cpe:2.3:o:microsoft:windows_server_2016:*:*:*:*:*:*:*:* Versions before 10.0.14393.9612 Vulnerable ·Microsoft
- cpe:2.3:o:microsoft:windows_server_2019:*:*:*:*:*:*:*:* Versions before 10.0.17763.9376 Vulnerable ·Microsoft
- cpe:2.3:o:microsoft:windows_server_2022:*:*:*:*:*:*:x64:* Versions before 10.0.20348.5761 Vulnerable ·Microsoft
- cpe:2.3:o:microsoft:windows_server_2025:*:*:*:*:*:*:x64:* Versions before 10.0.26100.33650 Vulnerable ·Microsoft
Remediation
Apply the fixed versions for each product: Windows Server 2012 R2 and its Server Core installation 6.3.9600.23470, Windows Server 2016 and its Server Core installation 10.0.14393.9612, Windows Server 2019 and its Server Core installation 10.0.17763.9376, Windows Server 2022 10.0.20348.5761, and Windows Server 2025 and its Server Core installation 10.0.26100.33650.
Written with Claude Haiku 5.5 from the sources below · 2026-10-28
- Fix · CNA Windows Server 2012 R2 (Microsoft) Fixed in 6.3.9600.23470
- Fix · CNA Windows Server 2012 R2 (Server Core installation) (Microsoft) Fixed in 6.3.9600.23470
- Fix · CNA Windows Server 2016 (Microsoft) Fixed in 10.0.14393.9612
- Fix · CNA Windows Server 2016 (Server Core installation) (Microsoft) Fixed in 10.0.14393.9612
- Fix · CNA Windows Server 2019 (Microsoft) Fixed in 10.0.17763.9376
- Fix · CNA Windows Server 2019 (Server Core installation) (Microsoft) Fixed in 10.0.17763.9376
- Fix · CNA Windows Server 2022 (Microsoft) Fixed in 10.0.20348.5761
- Fix · CNA Windows Server 2025 (Microsoft) Fixed in 10.0.26100.33650
- Fix · CNA Windows Server 2025 (Server Core installation) (Microsoft) Fixed in 10.0.26100.33650
Timeline
- 2026-10-13 Threatist record created from CVE-2026-85321
- 2026-10-13 Alias added: GHSA-6qx8-6vhq-mgfc
- 2026-10-14 Priority changed: LOW → MEDIUM
More Microsoft Windows Server 2012 vulnerabilities
- TI-2025-36863 Windows Server Update Service (WSUS) Remote Code Execution Vulnerability KEVCVSS 3.1CRITICAL 9.8
- TI-2020-01431 Netlogon Elevation of Privilege Vulnerability KEVCVSS 3.1CRITICAL 10.0
- TI-2020-01310 Improper input validation in Microsoft Windows Server KEVCVSS 3.1CRITICAL 10.0
- TI-2017-06077 Microsoft Windows XP SP3, Windows XP x64 XP2, Windows Server 2003 SP2, Windows Vista… KEVCVSS 3.1CRITICAL 9.8
- TI-2015-01465 HTTP.sys in Microsoft Windows 7 SP1, Windows Server 2008 R2 SP1, Windows 8, Windows 8.1… KEVCVSS 3.1CRITICAL 9.8
- TI-2020-01009 Improper input validation in Microsoft Windows Server KEVCVSS 3.1CRITICAL 9.0
Sources
- CVE-2026-85321 · CVE Program
- CVE-2026-85321 · NVD
- FIRST EPSS
- GHSA-6qx8-6vhq-mgfc · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences