CVE-2026-83645: Active Directory Federation Services (AD FS) Denial of Service Vulnerability
Active Directory Federation Services (AD FS) Denial of Service Vulnerability
Other sources
Allocation of resources without limits or throttling in Active Directory Federation Services (AD FS) allows an unauthorized attacker to deny service over a network.
— Microsoft
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 10.0.20348.5761Patch KB5126655 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 10.0.26100.33650Patch KB5126646 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 10.0.17763.9376Patch KB5126651 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 10.0.14393.9612Patch KB5126868 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 6.2.9200.26434Patch KB5126835 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 6.3.9600.23470Patch KB5126836
Event History
Frequently Asked Questions
Does an attacker need credentials or user interaction to exploit this issue?
No. The supplied vector indicates network-based exploitation with no privileges required and no user interaction required.
Which environments should be reviewed for exposure?
Review AD FS deployments on the listed Microsoft Windows platforms: Windows 10 and Windows Server 2012, 2012 R2, 2016, 2019, 2022, and 2025. Systems running Microsoft Active Directory Federation Services are also listed as affected.
Is the reported impact limited to availability?
Based on the supplied vector, the impact is high availability impact, with no reported confidentiality or integrity impact.