EUVD-2026-44134
GHSA-56v6-8mpw-v7h3
Severity by source
AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N
Admin-level authorization confirmed prerequisite (PR:H); network-facing AD FS web portal (AV:N); XSS inherently changes scope to victim's browser (S:C); no availability impact applies.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
2DescriptionCVE.org
Improper neutralization of input during web page generation ('cross-site scripting') in Active Directory Federation Services (AD FS) allows an authorized attacker to perform spoofing over a network.
AnalysisAI
Cross-site scripting in Active Directory Federation Services (AD FS) on Windows Server 2012 through 2025 enables an authorized, high-privileged attacker to inject malicious scripts into AD FS web pages, producing spoofing effects against users who interact with the affected portal. The CVSS vector (PR:H, UI:R, S:C) confirms this is a post-compromise capability requiring admin-level access and victim interaction, not an unauthenticated initial access vector. No active exploitation is confirmed - SSVC rates exploitation as 'none', EPSS sits at 0.38% (30th percentile), and the vulnerability is absent from CISA KEV - placing this firmly in the low-urgency category despite network reachability of the AD FS web interface.
Technical ContextAI
Active Directory Federation Services is Microsoft's claims-based identity federation component, embedded in Windows Server and used extensively in enterprise single-sign-on and hybrid Azure AD environments. CWE-79 (Improper Neutralization of Input During Web Page Generation) indicates that attacker-controlled data is reflected or stored into the HTML output of the AD FS web interface without adequate encoding or sanitization. The CVSS Scope:Changed metric is characteristic of XSS: the vulnerable component is the server-side AD FS application, but the exploitable impact lands in the victim's browser - a different security scope. CPE strings identify affected products as Windows Server 2012, 2012 R2, 2016, 2019, 2022, 2025 (including Server Core variants) and Windows 10 versions 1607 and 1809, all under the Microsoft application namespace (cpe:2.3:a:microsoft:...).
RemediationAI
Apply the vendor-released patch via Windows Update or WSUS targeting the fixed builds documented by ENISA EUVD-2026-44134: Windows Server 2025 to build 10.0.26100.33158 or later, Windows Server 2022 to 10.0.20348.5386 or later, Windows Server 2019 and Windows 10 1809 to 10.0.17763.9020 or later, Windows Server 2016 and Windows 10 1607 to 10.0.14393.9339 or later, Windows Server 2012 R2 to 6.3.9600.23291 or later, and Windows Server 2012 to 6.2.9200.26226 or later. The full advisory is at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-50684. If patching is not immediately possible, restrict administrative access to the AD FS management console and claims-rule editing interfaces to a minimal set of trusted accounts using tiered privileged access workstations (PAWs); this directly eliminates the PR:H attack surface. Additionally, enable AD FS audit logging and monitor for unexpected changes to relying party configurations or claim transformation rules, which is where injected content would most likely be introduced.
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External POC / Exploit Code
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