Description

Concurrent execution using shared resource with improper synchronization ('race condition') in Windows DNS allows an unauthorized attacker to execute code over a network.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "8.1",
  "pubDate": "2026-08-11T17:18:36.177Z",
  "pubdate": "2026-08-11T17:18:36.177Z",
  "executiveSummary": "A vulnerability classified as a concurrent execution using shared resource with improper synchronization, commonly known as a race condition, has been identified in Windows DNS. This security flaw enables an unauthorized, remote network attacker to achieve arbitrary code execution on targeted systems.\nThe vulnerability directly impacts the Windows DNS service, exposing enterprise networks and domain infrastructures to severe compromise. An attacker capable of interacting with the DNS service over the network can exploit timing discrepancies during shared resource access.\nSuccessful exploitation allows the execution of arbitrary code with the privileges of the DNS service, which typically runs with elevated system privileges. This grants the attacker deep access to the underlying operating system, facilitating lateral movement, data exfiltration, or complete system takeover.\nThe attack vector is network-based, meaning exploitation does not inherently require physical access or prior authentication, lowering the barrier for potential threat actors. Remediation requires applying official vendor patches specifically addressing the improper synchronization flaw within the DNS subsystem.",
  "technicalDetails": "The root cause of the vulnerability resides in the Windows DNS component's handling of concurrent execution threads accessing shared memory resources without adequate synchronization primitives. When multiple network requests or internal threads attempt to read, write, or modify these shared data structures simultaneously, a race condition occurs.\nAn attacker triggers this vulnerability by sending specifically crafted network packets to the Windows DNS service over the network. These packets are designed to intersect with specific execution windows where resource locks are absent or improperly implemented, leading to race conditions such as Time-of-Check to Time-of-Use (TOCTOU) anomalies or memory corruption states.\nThe attack flow begins with the network exposure of the Windows DNS service listening on standard ports. The attacker transmits asynchronous or high-frequency requests designed to manipulate internal object states while the service processes concurrent operations. Due to the lack of proper mutexes, semaphores, or critical sections protecting the shared resource, the application encounters an inconsistent state.\nThis inconsistent state can manifest as dangling pointers, double-frees, or heap corruption within the memory space managed by the DNS service. By carefully timing the requests and grooming the heap, the attacker can influence the memory layout to translate the synchronization flaw into reliable arbitrary code execution.\nBecause the Windows DNS service executes in a privileged context, successfully executed payloads inherit these elevated privileges, bypassing standard user-mode restrictions. Post-exploitation impact includes the installation of persistent backdoors, manipulation of DNS records for redirection attacks, and compromise of Active Directory environments where DNS is integrated."
}