CVE-2026-85321: 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 10.0.26100.33650Patch KB5126646 - 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 6.3.9600.23470Patch KB5126836 - 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 10.0.17763.9376Patch KB5126651
Event History
Frequently Asked Questions
Who is exposed to this issue?
Organizations running AD FS on the listed Microsoft Windows Server versions are exposed. Because the attack vector is network-based and requires no privileges or user interaction, an unauthenticated remote attacker can target reachable AD FS services.
What does an attacker need to exploit it?
The attacker needs network access to the affected AD FS service. The available data indicates low attack complexity, no authentication or privileges, and no user interaction are required.
What is the expected impact of exploitation?
Successful exploitation can deny service by causing AD FS to allocate resources without limits or throttling. The provided severity vector indicates availability impact only, with no stated confidentiality or integrity impact.