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": "2026-08-11T17:18:24.847Z",
  "pubdate": "2026-08-11T17:18:24.847Z",
  "executiveSummary": "A local privilege escalation vulnerability exists in the Windows Telephony Service, categorized under CWE-362: Concurrent Execution Using Shared Resource with Improper Synchronization (Race Condition).\nThis vulnerability allows an authorized local attacker to elevate their execution privileges on affected systems.\nThe flaw stems from improper handling of shared resources during concurrent execution threads within the telephony service component.\nExploitation requires the attacker to have local access and the ability to execute code on the target machine, lowering the initial barrier if compromised execution occurs via a standard user context.\nSuccessful exploitation results in unauthorized privilege elevation, potentially granting the attacker higher-level system access, such as administrative or SYSTEM-equivalent privileges, depending on the service execution context.\nThe risk implication is severe for multi-user environments or systems where privilege boundary enforcement is critical, as a low-privileged user can subvert security controls to compromise the underlying operating system integrity.",
  "technicalDetails": "The vulnerability resides in the Windows Telephony Service, specifically within routines that handle shared system resources across multiple concurrent execution threads without proper synchronization mechanisms.\nThe root cause is a classic race condition (CWE-362), where the state of a shared resource is checked and subsequently modified across asynchronous operations without atomic guarantees or appropriate locking primitives such as mutexes or critical sections.\nThe affected component is the Windows Telephony Service subsystem, which executes with elevated system privileges.\nAn authorized local attacker leverages this concurrency flaw by manipulating the timing and execution of specific inter-process communications or internal service requests.\nThe step-by-step attack flow involves the attacker initiating concurrent requests to the Windows Telephony Service designed to target the vulnerable shared resource.\nDue to the absence of proper synchronization, a time-of-check to time-of-use (TOCTOU) discrepancy occurs, allowing the attacker to interleave malicious state changes between the validation phase and the operational execution phase of the service.\nBy winning the race condition, the attacker can induce memory corruption, unauthorized object manipulation, or arbitrary write primitives within the context of the running service.\nAuthentication requirements dictate that the attacker must already possess local access to the system, typically as an authorized low-privileged user.\nNetwork exposure is non-existent for this vector, as the attack surface is strictly local.\nPost-exploitation impact includes local privilege escalation, enabling the execution of arbitrary code with the elevated privileges of the Windows Telephony Service, thereby bypassing standard security descriptor constraints and facilitating complete system compromise."
}