High MSRC-CVE-2026-83646 1 CVE

Active Directory Federation Services (AD FS) Spoofing Vulnerability

Published Oct 13, 2026 · Updated Oct 13, 2026

Vendor: Microsoft

Summary

Impact: Spoofing. Microsoft rating: Important. Not known to be exploited — Exploitation Unlikely. Customer action: Required.

Details

Security updates
10.0.17763.9376 — https://support.microsoft.com/help/5126651
10.0.20348.5761 — https://support.microsoft.com/help/5126655
10.0.26100.33650 — https://support.microsoft.com/help/5126646
10.0.14393.9612 — https://support.microsoft.com/help/5126868

Vulnerabilities 1

Medium 4.8

CVE-2026-83646

Active Directory Federation Services (AD FS) Spoofing Vulnerability

Url redirection to untrusted site ('open redirect') in Active Directory Federation Services (AD FS) allows an authorized attacker to perform spoofing over a network.

Microsoft Windows Server 2019 Windows Server 2019 (Server Core installation) Windows 10 Version 1809 Windows

Oct 13, 2026

Revision history

2026-10-13 #1
Information published.

References

CVE-2026-83646 Active Directory Federation Services (AD FS) Spoofing Vulnerability - HTML
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-83646
Microsoft Exploitability Index
https://www.microsoft.com/en-us/msrc/exploitability-index?rtc=1
Microsoft Support Lifecycle
https://support.microsoft.com/lifecycle
Common Vulnerability Scoring System
https://www.first.org/cvss