Description

Heap-based buffer overflow in Windows Telephony Service allows an authorized attacker to elevate privileges locally.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.8",
  "pubDate": "2026-08-11T17:18:09.983Z",
  "pubdate": "2026-08-11T17:18:09.983Z",
  "executiveSummary": "This vulnerability is a heap-based buffer overflow affecting the Windows Telephony Service. The flaw arises from improper bounds checking during the processing of telephony data within the affected component. Successfully exploiting this vulnerability enables an authenticated local attacker to execute arbitrary code with elevated system privileges.\nThe affected system is the Windows Telephony Service across supported configurations where the service processes specially crafted local inputs. The risk implications are severe, as local privilege escalation typically transitions a standard user context to a highly privileged administrative or SYSTEM context, bypassing core operating system security boundaries.\nAttacker capabilities are constrained by local execution requirements, necessitating that the threat actor possesses valid credentials and the ability to interact locally or via a pre-established execution vector on the target host. Exploitation requirements include the successful execution of malicious code designed to trigger the heap corruption condition within the memory space of the vulnerable service.",
  "technicalDetails": "The root cause of the vulnerability resides in a heap-based buffer overflow within the Windows Telephony Service. Specifically, the vulnerable component fails to adequately validate the size of input data copied into dynamically allocated heap memory buffers. When a specially crafted request or data structure is supplied to the service, the copy operation exceeds the allocated boundaries of the target heap chunk, resulting in adjacent memory corruption.\nThe vulnerable component is the internal routing or data handling subsystem of the Windows Telephony Service, which processes client requests locally. The flaw can be triggered by an authenticated user who interacts with the service APIs or inter-process communication channels exposed by the telephony architecture. Because the service typically executes with high privileges, corrupting the heap allows an attacker to manipulate internal data structures, function pointers, or objects residing in adjacent heap memory.\nThe attack flow proceeds as follows: First, the authenticated attacker authenticates locally on the target system. Second, the attacker formulates a malicious payload designed to interact with the Windows Telephony Service. Third, the attacker invokes the vulnerable API or communication interface, passing the oversized or malformed data structure into the service context. Fourth, the service attempts to process the input, resulting in an unsafe memory copy operation that overflows the target heap buffer. Finally, the attacker leverages the resulting heap corruption to overwrite critical function pointers or control data, hijacking the execution flow of the service.\nThe privilege requirements mandate that the attacker must be authorized to interact with the local service, though the required privilege level is generally that of a standard authenticated user. The network exposure is strictly local, as the attack vector does not inherently expose a remote network interface for exploitation without prior local access or pivoting.\nThe post-exploitation impact includes full local privilege escalation. Upon successful control flow hijacking via heap corruption, the attacker can execute arbitrary commands or payloads inheriting the security context of the Windows Telephony Service, thereby achieving SYSTEM-level access and complete compromise of the underlying operating system."
}