CVE-2026-62729 in Windows
Summary
by MITRE • 08/11/2026
Concurrent execution using shared resource with improper synchronization ('race condition') in Windows Telephony Service allows an authorized attacker to elevate privileges locally.
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Analysis
by VulDB Data Team • 08/12/2026
A critical race condition vulnerability exists within the Windows Telephony Service that enables authenticated attackers to achieve local privilege escalation through improper synchronization of shared resources during concurrent execution. This flaw resides in the telephony service component responsible for managing telephone communications and system integration functions. The vulnerability manifests when multiple threads or processes attempt to access and modify shared telephony service resources simultaneously without adequate locking mechanisms or synchronization protocols, creating temporal windows where malicious code can exploit inconsistent states.
The technical implementation of this race condition occurs at the kernel level within Windows Telephony Service functionality, where resource allocation and state management operations lack proper atomicity guarantees. When legitimate system processes or user applications interact with telephony service APIs concurrently, the absence of mutex locks or critical section guards allows for interleaved execution patterns that can be manipulated by an attacker. This improper synchronization creates opportunities for privilege escalation attacks through techniques such as heap spraying, object reuse, or manipulation of shared data structures that control access control decisions.
The operational impact of this vulnerability extends beyond simple local privilege escalation to potentially compromise entire system security postures. An authenticated user with minimal privileges can leverage this race condition to gain SYSTEM-level access without requiring additional attack vectors or complex exploitation techniques. The attack surface includes scenarios where telephony services are actively utilized, such as during phone call establishment, fax processing, or modem communication operations. Security researchers have identified that this vulnerability aligns with CWE-362, which specifically addresses race conditions in concurrent programming environments.
The practical exploitation of this vulnerability requires an attacker to carefully time their malicious code execution to coincide with legitimate telephony service operations, taking advantage of the temporal gap between resource allocation and deallocation phases. This attack pattern falls under ATT&CK technique T1068, which covers local privilege escalation through race conditions and synchronization flaws. The Windows Telephony Service component presents an ideal target for such attacks due to its persistent nature and elevated privileges required for core telephony operations.
Mitigation strategies should focus on implementing proper synchronization primitives throughout the telephony service codebase, including mutex locks, semaphores, or atomic operations to prevent concurrent access to shared resources. System administrators should ensure timely application of Microsoft security patches that address this specific race condition vulnerability. Additionally, implementing runtime protections such as control flow integrity checks and exploit mitigation techniques can reduce the effectiveness of potential exploitation attempts. The vulnerability demonstrates the critical importance of proper concurrent programming practices in system-level services where privilege escalation opportunities can arise from seemingly benign synchronization issues.