Stack-based Buffer Overflow in Active Directory Federation Services

Executive Summary

CVE-2026-50304 is a stack-based buffer overflow vulnerability in Microsoft Active Directory Federation Services (AD FS). This flaw allows an unauthorized attacker to send specially crafted input over a network, causing a buffer overflow in the service.

A buffer overflow occurs when a program writes more data to a buffer than it can hold, leading to memory corruption. In this case, the overflow can cause the AD FS service to crash or become unresponsive, resulting in a denial of service (DoS).

The vulnerability does not require authentication (PR:N) and can be exploited remotely (AV:N), making it accessible to attackers over the internet or a local network.

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Impact Analysis

This vulnerability can impact you in the following ways:

• Denial of Service (DoS): An attacker can exploit this flaw to crash or disrupt the Active Directory Federation Services, preventing legitimate users from accessing federated authentication services.
• Service Outages: If AD FS is critical for your organization's authentication workflows (e.g., single sign-on or cloud-based applications), its unavailability can halt business operations.
• Potential for Further Exploitation: While this CVE is classified as a DoS, buffer overflow vulnerabilities can sometimes be leveraged for remote code execution (RCE) in other scenarios, though this is not confirmed for CVE-2026-50304.

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Compliance Impact

This vulnerability may affect compliance with common standards and regulations in the following ways:

• GDPR (General Data Protection Regulation): If AD FS is used to authenticate access to personal data, a DoS attack could disrupt data availability, potentially violating GDPR's requirement for ensuring the availability and resilience of processing systems (Article 32).
• HIPAA (Health Insurance Portability and Accountability Act): For organizations handling protected health information (PHI), AD FS downtime could prevent access to critical systems, leading to non-compliance with HIPAA's availability and security requirements (e.g., Security Rule §164.308(a)(7)).
• Other Standards: Frameworks like ISO 27001 or NIST SP 800-53 emphasize the need for system availability and resilience. A DoS vulnerability could indicate a failure to implement adequate controls (e.g., ISO 27001 A.12.2.1 or NIST AC-17).

However, the specific impact on compliance depends on how AD FS is used in your environment and whether the vulnerability leads to actual disruptions or data breaches.

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Mitigation Strategies

Apply the security update provided by Microsoft for CVE-2026-50304. This update addresses the stack-based buffer overflow in Active Directory Federation Services and mitigates the denial of service risk.

• Visit the Microsoft Security Response Center (MSRC) update guide for CVE-2026-50304 to download and install the patch.
• Ensure all systems running Active Directory Federation Services are updated to the latest secure version.
• Monitor Microsoft's official communications for any additional guidance or updates related to this vulnerability.

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