Description

Use after free in Windows Telephony Service allows an authorized attacker to elevate privileges locally.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.8",
  "pubDate": "2026-08-11T17:18:19.867Z",
  "pubdate": "2026-08-11T17:18:19.867Z",
  "executiveSummary": "A use-after-free vulnerability exists within the Windows Telephony Service, affecting local Microsoft Windows environments. This memory corruption flaw allows an authorized local attacker to execute arbitrary code and achieve local privilege escalation. The vulnerability arises from improper handling of object lifecycles in memory, specifically when resources are accessed after they have been freed or deallocated. Successful exploitation of this security defect compromises the integrity and confidentiality of the host operating system, potentially allowing the threat actor to gain elevated privileges such as SYSTEM access depending on the context of the vulnerable service process. Attacker capabilities require prior local access to the target system and valid authorization to interact with the telephony component. Mitigation relies heavily on applying official vendor patches as they become available to correct the underlying memory management defect within the affected Windows component.",
  "technicalDetails": "The vulnerability is a classic use-after-free (UAF) condition residing in the Windows Telephony Service component. The root cause stems from flaws in dynamic memory allocation and deallocation routines, where a pointer to a specific telephony object is not appropriately nullified or managed after the underlying memory structure is freed. Consequently, dangling pointers remain accessible to specific execution threads.\nThe attack flow begins when an authorized local attacker interacts with the Windows Telephony Service application programming interfaces (APIs) or Inter-Process Communication (IPC) mechanisms exposed by the service. By sending a carefully crafted sequence of requests, the attacker forces the service to deallocate a specific memory object while retaining a reference to it. Subsequently, the attacker triggers a secondary operation that references the dangling pointer, resulting in the manipulation of freed heap memory.\nThrough heap grooming and precise timing techniques, the attacker can allocate controlled payload data into the exact memory location previously occupied by the freed telephony object. When the service subsequently accesses the dangling pointer, it executes attacker-controlled data, such as function pointers or vtable entries, leading to arbitrary code execution within the security context of the service process.\nThe vulnerable component is executed locally and requires the attacker to possess local access and authorization to interface with the telephony subsystem. Because the Windows Telephony Service frequently operates with high privileges, successful memory manipulation and code execution directly result in local privilege escalation. Network exposure is typically non-existent unless combined with other remote vectors, as the attack surface is exposed locally via documented service interfaces. Post-exploitation impact includes full system compromise, installation of persistent backdoors, and bypassing local security controls."
}