CVE-2026-85324 in Windows
Summary
by MITRE • 10/14/2026
Memory allocation with excessive size value in Active Directory Federation Services (AD FS) allows an unauthorized attacker to deny service over a network.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability identified within Active Directory Federation Services represents a critical flaw in the memory management subsystem, specifically involving improper validation of input parameters during resource allocation requests. This issue stems from a failure by the application to adequately verify that size values provided by clients are within acceptable bounds before attempting to allocate corresponding amounts of system memory. When an attacker submits a request containing an excessively large size value, the AD FS service attempts to reserve a disproportionately large block of virtual or physical memory on the server host. This behavior deviates from secure coding standards which mandate rigorous input sanitization and boundary checks prior to any dynamic memory allocation operations. The root cause is classified under CWE-789 as Memory Allocation with Excessive Size Value, indicating that the software does not restrict or incorrectly restrict allocations of resources based on size, leading to potential system instability or failure.
From an operational perspective, this flaw enables a remote unauthenticated attacker to trigger a denial-of-service condition against the AD FS infrastructure without requiring valid credentials. By repeatedly sending crafted requests with oversized allocation parameters, the attacker can exhaust available memory resources on the server hosting the federation service. This resource exhaustion causes the application process to become unresponsive or crash entirely, effectively halting authentication and authorization services for all users relying on that specific identity provider. The impact is severe as AD FS often serves as a central point of trust in enterprise environments; its disruption can cascade into broader organizational outages affecting single sign-on capabilities, access control systems, and dependent applications that rely on tokens issued by the compromised service.
This vulnerability aligns with MITRE ATT&CK technique T1498 Network Denial of Service, specifically sub-technique T1498.002 Resource Exhaustion via Flood Attacks, as it involves overwhelming system resources to degrade availability rather than compromising confidentiality or integrity directly. The attack vector is typically remote and network-based, allowing adversaries located outside the protected perimeter to exploit this weakness through standard HTTP/S traffic directed at AD FS endpoints. There are no known mitigations such as patches available for older versions of Windows Server where AD FS resides, making proactive defense strategies essential. Organizations should implement strict rate limiting on authentication endpoints, deploy web application firewalls capable of detecting and blocking anomalous request sizes or frequencies, and ensure that server configurations include memory limits to prevent any single process from consuming all available system resources. Regular monitoring for unusual spikes in memory usage associated with AD FS processes can also aid in early detection and response to exploitation attempts.