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": "2026-08-11T17:18:06.090Z",
  "pubdate": "2026-08-11T17:18:06.090Z",
  "executiveSummary": "A privilege escalation vulnerability exists in the Windows Telephony Service due to concurrent execution using a shared resource with improper synchronization, commonly categorized as a race condition. This flaw enables an authorized local attacker to manipulate shared system resources during execution windows where synchronization is absent, ultimately leading to an elevation of privileges on the affected operating system. The vulnerability impacts the Windows Telephony Service component across specified Windows environments. The primary risk implication centers on the potential for a localized low-privileged threat actor to escalate their execution context to higher administrative privilege levels, bypassing intended access controls. Exploitation of this vulnerability requires local access to the target system and an existing authorization context, meaning an attacker must already possess the ability to execute code locally prior to initiating the race condition sequence. No specific remote network exposure is detailed, classifying this strictly as a local vector. Remediation relies upon applying official vendor patches designed to implement proper locking mechanisms and synchronization primitives within the vulnerable service code.",
  "technicalDetails": "The vulnerability resides within the Windows Telephony Service, specifically stemming from a design flaw involving concurrent execution using a shared resource with improper synchronization. At the root cause level, the service fails to adequately protect shared data structures or memory regions during multi-threaded operations, leaving a temporal window where asynchronous execution can introduce race conditions. The vulnerable component is the internal routine managing shared telephony resources within the service architecture. To exploit this condition, an authorized local attacker must initiate a sequence of operations designed to interact with the Windows Telephony Service while simultaneously generating high-frequency concurrent requests or conflicting resource modifications. By timing these interactions precisely to intercept the resource state during the unprotected operational window between validation and actual usage (TOCTOU-style or general race condition mechanics), the attacker can induce memory corruption, state inconsistency, or unauthorized resource manipulation. Given that the affected service typically executes with elevated system privileges, successfully winning the race condition allows the attacker to hijack the execution flow or corrupt operational data in a manner that forces the service to perform actions on behalf of the attacker with heightened privileges. Authentication requirements dictate that the attacker must possess valid local execution capabilities, and the attack surface is exposed locally rather than remotely over a network protocol. Post-exploitation impact resulting from this privilege escalation includes full local system compromise, enabling the attacker to install arbitrary applications, view, change, or delete data, and create new accounts with full user rights depending on the resultant privilege level achieved."
}