Description

Use after free in Windows Failover Cluster allows an unauthorized attacker to execute code over a network.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "9.8",
  "pubDate": "2026-09-08T18:20:29.987Z",
  "pubdate": "2026-09-08T18:20:29.987Z",
  "executiveSummary": "A critical use-after-free vulnerability exists within the Windows Failover Cluster component, exposing the system to potential remote code execution (RCE).\nThe vulnerability occurs due to improper memory management, where the application continues to reference a memory address after the resource has been freed.\nSuccessful exploitation allows an unauthorized, unauthenticated network attacker to execute arbitrary code with elevated privileges on the target system.\nThis flaw represents a significant risk to organizational infrastructure, as Windows Failover Clusters are typically deployed in high-availability environments where compromise could result in complete cluster takeover, unauthorized data access, and lateral movement within the network.\nThe exploit does not require prior authentication, making the attack vector highly dangerous as it can be triggered remotely by sending specially crafted network packets to the vulnerable service.\nImmediate mitigation is required to prevent unauthorized system control.",
  "technicalDetails": "The vulnerability is a classic use-after-free (UAF) condition residing in the Windows Failover Cluster service. This class of memory corruption occurs when a program continues to use a pointer to a memory location after the dynamic memory associated with that pointer has been deallocated or freed.\nIn the context of the Failover Cluster component, the service fails to properly synchronize the lifecycle of certain objects during the processing of specific network requests. The vulnerable component fails to nullify or reset the pointer after the memory is released to the heap allocator.\nThe exploitation flow typically follows these steps: First, the attacker sends a sequence of maliciously crafted network packets designed to trigger the allocation and subsequent premature deallocation of a specific object within the cluster's memory heap. Due to race conditions or incorrect state handling during the object cleanup phase, the service maintains a dangling pointer to the deallocated memory region.\nSecond, the attacker leverages a technique known as heap spraying or heap grooming to reallocate the freed memory block with controlled data. By filling the recently freed memory area with a malicious payload—such as a ROP chain or shellcode—the attacker ensures that when the application subsequently attempts to perform an operation using the dangling pointer, it inadvertently executes the attacker-supplied data.\nBecause the Windows Failover Cluster service often runs with high system or administrative privileges, successful redirection of the instruction pointer (EIP/RIP) allows the attacker to achieve full control over the execution flow. The impact of this vulnerability is total system compromise, as the injected code operates within the security context of the service.\nThe vulnerability is reachable over the network without requiring valid credentials. The lack of authentication constraints means that any node or attacker with network visibility to the cluster's management interfaces can potentially initiate the exploit sequence. The post-exploitation phase includes the capability to install persistent backdoors, dump sensitive credentials from memory (e.g., via LSASS interaction), or propagate the attack to other nodes within the cluster architecture."
}