Description

Concurrent execution using shared resource with improper synchronization ('race condition') in Windows Telephony Service allows an authorized attacker to elevate privileges locally.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.0",
  "pubDate": "2026-08-19T21:17:08.730Z",
  "pubdate": "2026-08-19T21:17:08.730Z",
  "executiveSummary": "A local privilege escalation vulnerability exists within the Windows Telephony Service, specifically arising from concurrent execution using a shared resource with improper synchronization, commonly categorized as a race condition. The vulnerability affects the Windows Telephony Service component across specified Windows operating system environments. Successful exploitation of this flaw allows an authorized local attacker to elevate their execution privileges on the targeted system, potentially granting unauthorized administrative or SYSTEM-level control. The risk implication is significant as it facilitates lateral movement or deeper system compromise from a standard user context. Exploitation requirements dictate that the attacker must already possess local access to the target host and the ability to interact with the vulnerable service mechanism. The attack vector is strictly local, requiring no specialized network exposure or remote interaction. Mitigation relies on applying official vendor patches as soon as they become available and enforcing strict local access controls to restrict unauthorized code execution.",
  "technicalDetails": "The root cause of the vulnerability resides in the improper synchronization of shared resources during concurrent execution threads within the Windows Telephony Service. When multiple threads access or modify shared memory or critical state variables without adequate locking mechanisms or mutual exclusion primitives, a race condition occurs. This architectural flaw introduces a temporal window of vulnerability between the validation phase and the operational use of the shared resource, commonly referred to as Time-of-Check to Time-of-Use (TOCTOU). To exploit this condition, an authorized local attacker initiates concurrent requests or operations designed to manipulate the shared resource state during the precise execution window managed by the vulnerable component. By winning the race condition, the attacker can cause the service to perform operations on unintended objects, corrupt memory structures, or bypass standard security checks. The vulnerable component is the internal routine of the Windows Telephony Service responsible for managing concurrent client requests and shared state resources. Authentication requirements dictate that the attacker must possess valid local credentials to interact with the service interface. Privilege requirements are limited to standard local user access, as the vulnerability enables privilege escalation from low-integrity or medium-integrity contexts to higher privilege tiers. Network exposure is non-existent, as the flaw is confined to local Inter-Process Communication (IPC) or local service APIs. The post-exploitation impact includes arbitrary code execution with elevated privileges, allowing the adversary to disable security controls, access sensitive system files, or establish persistent unauthorized access across the compromised operating system."
}