CVE-2026-96252: Active Directory Federation Services (AD FS) Spoofing Vulnerability

Overview

Severity

Critical (CVSS 9.1)

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N/E:U/RL:O/RC:C

Category

Spoofing

Exploit Status

Not Exploited

Exploitation Likelihood

Less Likely

Patch Tuesday

2026-Oct

Released

2026-10-13

EPSS Score

0.48% (percentile: 39.9%)

Description

Improper verification of cryptographic signature in Active Directory Federation Services (AD FS) allows an unauthorized attacker to perform spoofing over a network.

FAQ

How could an attacker exploit this vulnerability? An unauthenticated attacker could relay a validly signed SAML response intended for a different endpoint to an affected AD FS endpoint. Successful exploitation could allow the attacker to create an unauthorized session and obtain tokens. No user interaction is required.

Affected Products (16)

ESU

• Windows Server 2012
• Windows Server 2012 (Server Core installation)
• Windows Server 2012 R2
• Windows Server 2012 R2 (Server Core installation)

Windows

• Windows Server 2016
• Windows Server 2016 (Server Core installation)
• Windows Server 2019
• Windows Server 2019 (Server Core installation)
• Windows Server 2022
• Windows Server 2022 (Server Core installation)
• Windows Server 2025
• Windows Server 2025 (Server Core installation)
• Windows 10 Version 1607 for 32-bit Systems
• Windows 10 Version 1607 for x64-based Systems
• Windows 10 Version 1809 for 32-bit Systems
• Windows 10 Version 1809 for x64-based Systems

Security Updates (6)

• 5126835
• 5126836
• 5126868
• 5126651
• 5126655
• 5126646

Revision History

• 2026-10-13: Information published.