Description

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

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "9.8",
  "pubDate": "2026-09-08T18:19:45.140Z",
  "pubdate": "2026-09-08T18:19:45.140Z",
  "executiveSummary": "This vulnerability is identified as a Use-After-Free (UAF) memory corruption flaw residing within the Windows DNS service.\nThe defect allows a remote, unauthenticated attacker to execute arbitrary code with elevated privileges on an affected system.\nThe vulnerability occurs when the Windows DNS service improperly handles objects in memory, leading to a state where the service attempts to access a memory location after the associated object has been deallocated.\nBy sending specially crafted network packets to the targeted Windows DNS server, an attacker can trigger this memory mismanagement, potentially leading to remote code execution (RCE).\nThe risk is critical due to the core nature of the DNS service, which typically runs with SYSTEM privileges, and the lack of requirement for user interaction or prior authentication.\nSuccessful exploitation compromises the integrity, availability, and confidentiality of the host, enabling attackers to install malicious software, manipulate data, or pivot through the internal network.",
  "technicalDetails": "The root cause of this vulnerability is a Use-After-Free (UAF) condition within the Windows DNS service's memory management logic. A UAF vulnerability occurs when a program continues to use a pointer to a memory location after that memory has been freed or reallocated.\nIn the context of the Windows DNS service, the vulnerability manifests during the processing of malformed DNS packets. When the service performs internal operations—such as parsing resource records or handling complex queries—it may prematurely free an object while retaining a reference (dangling pointer) to that memory address in a global or static control block.\nThe attack flow initiates when an attacker transmits a maliciously constructed network packet targeting the DNS service port (typically UDP/TCP 53). As the service processes the packet, the vulnerable code path is triggered, causing a specific object to be deallocated. Subsequently, the service's execution flow attempts to access this object again using the dangling pointer.\nAn attacker can exploit this by engaging in heap grooming or heap spraying techniques. Before triggering the 'use' phase of the UAF, the attacker attempts to allocate new data at the memory address previously occupied by the freed object. By filling this space with controlled, malicious data—specifically a fake object structure containing crafted function pointers or vtable entries—the attacker forces the DNS service to redirect its execution flow when it subsequently dereferences the dangling pointer.\nBecause the DNS service operates within the context of the NT AUTHORITY\\SYSTEM account, successful control over the execution flow results in arbitrary code execution at the highest privilege level on the local machine. This bypasses typical user-mode security boundaries and provides the attacker full control over the operating system environment.\nThe exploitation process requires no authentication and is remotely reachable over the network. Post-exploitation, the attacker may attempt to stabilize the process to avoid service crashes, establish a persistent foothold, or utilize the compromised system as a staging point for lateral movement within the enterprise network infrastructure."
}