CVE-2025-24056: Windows 10 1507 Buffer Overflow Vulnerability

CVE-2025-24056 Overview

CVE-2025-24056 is a heap-based buffer overflow vulnerability in the Windows Telephony Server that allows an unauthorized attacker to execute arbitrary code over a network. This memory corruption flaw (CWE-122) affects a wide range of Microsoft Windows operating systems, including both client and server editions spanning multiple versions from Windows Server 2008 to the latest Windows Server 2025.

The vulnerability exists within the Windows Telephony Service (TAPI), a core Windows component that provides telephony capabilities to applications. When exploited, an attacker can corrupt heap memory structures, potentially gaining complete control over the affected system with the privileges of the Telephony Service.

Critical Impact

Successful exploitation enables remote code execution over the network, allowing attackers to execute arbitrary code with elevated privileges on affected Windows systems without authentication.

Affected Products

• Microsoft Windows 10 (versions 1507, 1607, 1809, 21H2, 22H2)
• Microsoft Windows 11 (versions 22H2, 23H2, 24H2)
• Microsoft Windows Server 2008 SP2, 2008 R2 SP1, 2012, 2012 R2, 2016, 2019, 2022, 2022 23H2, 2025

Discovery Timeline

• March 11, 2025 - CVE-2025-24056 published to NVD
• July 2, 2025 - Last updated in NVD database

Technical Details for CVE-2025-24056

Vulnerability Analysis

The Windows Telephony Server vulnerability stems from improper bounds checking when processing incoming network requests. The heap-based buffer overflow occurs when the Telephony Service handles specially crafted data that exceeds the allocated heap buffer size, causing adjacent memory regions to be overwritten.

This vulnerability requires user interaction for successful exploitation, meaning an attacker would need to convince a user to open a malicious file or visit a compromised website that triggers the vulnerable code path. Despite this requirement, the impact is severe as it can lead to complete system compromise with full confidentiality, integrity, and availability impact.

The attack can be initiated remotely over the network with low complexity and requires no prior privileges on the target system, making it an attractive target for threat actors seeking initial access to enterprise environments.

Root Cause

The root cause of CVE-2025-24056 is a classic heap-based buffer overflow (CWE-122) in the Windows Telephony Server component. The vulnerability occurs due to insufficient validation of input length before copying data into a fixed-size heap buffer. When the service processes malformed telephony requests, it fails to properly verify that the incoming data fits within the allocated heap memory region, allowing an attacker to write beyond the buffer boundaries.

This type of memory corruption vulnerability can lead to arbitrary code execution by overwriting critical heap metadata or adjacent heap objects, enabling attackers to redirect program execution flow.

Attack Vector

The attack vector for this vulnerability is network-based. An attacker can exploit this vulnerability by sending specially crafted requests to the Windows Telephony Service. The exploitation scenario typically involves:

1. The attacker crafts a malicious payload designed to trigger the heap-based buffer overflow
2. The victim is enticed to interact with attacker-controlled content (malicious file or compromised website)
3. The payload is processed by the Windows Telephony Server, causing heap memory corruption
4. The attacker gains code execution in the context of the Telephony Service

The vulnerability mechanism involves sending oversized or malformed data to the Telephony Server that exceeds expected buffer allocations. When the service attempts to process this data without proper bounds checking, the heap buffer overflows, potentially corrupting adjacent heap structures and enabling arbitrary code execution. For detailed technical information, refer to the Microsoft Security Advisory.

Detection Methods for CVE-2025-24056

Indicators of Compromise

• Unexpected crashes or restarts of the Windows Telephony Service (TapiSrv)
• Anomalous network traffic targeting TAPI-related ports and services
• Unusual memory allocation patterns in the tapisrv.dll process
• Event log entries indicating heap corruption or access violations in telephony components

Detection Strategies

• Monitor Windows Event Logs for Telephony Service crashes or error events (Event IDs related to service failures)
• Deploy network intrusion detection signatures to identify malformed TAPI requests
• Utilize endpoint detection and response (EDR) solutions to monitor for suspicious process behavior associated with svchost.exe hosting the Telephony Service
• Implement memory integrity monitoring to detect heap corruption attempts

Monitoring Recommendations

• Enable verbose logging for the Windows Telephony Service to capture detailed request information
• Configure SIEM rules to alert on multiple Telephony Service restart events within a short timeframe
• Monitor for suspicious outbound network connections from telephony-related processes
• Deploy SentinelOne's behavioral AI to detect exploitation attempts and post-exploitation activities

How to Mitigate CVE-2025-24056

Immediate Actions Required

• Apply the latest Microsoft security updates addressing CVE-2025-24056 immediately
• If patching is not immediately possible, consider disabling the Windows Telephony Service on systems that do not require telephony functionality
• Implement network segmentation to limit exposure of vulnerable systems
• Review firewall rules to restrict access to telephony services from untrusted networks

Patch Information

Microsoft has released security updates to address this vulnerability. Organizations should apply the appropriate patches from the Microsoft Security Update Guide for CVE-2025-24056. The patches are available for all affected Windows versions, including Windows 10, Windows 11, and Windows Server editions. Organizations should prioritize patching based on system criticality and exposure.

Workarounds

• Disable the Windows Telephony Service (TapiSrv) on systems where telephony functionality is not required
• Implement network-level controls to block untrusted access to TAPI-related services
• Use Windows Firewall or external firewalls to restrict inbound connections to affected services
• Apply the principle of least privilege to limit the impact of potential exploitation

# Disable Windows Telephony Service (if not required)
sc config TapiSrv start= disabled
sc stop TapiSrv

# Verify the service is stopped
sc query TapiSrv