CVE-2024-43627 Overview
CVE-2024-43627 is a remote code execution vulnerability in the Windows Telephony Service affecting a broad range of Microsoft Windows client and server editions. The flaw is classified as a heap-based buffer overflow [CWE-122] and allows an attacker to execute arbitrary code in the context of the vulnerable service. Exploitation requires user interaction but no prior authentication, and the attack can be initiated over the network. The vulnerability impacts confidentiality, integrity, and availability, making it a high-priority issue for Windows estates.
Critical Impact
Successful exploitation allows attackers to execute arbitrary code on affected Windows hosts, potentially leading to full system compromise across desktop and server installations.
Affected Products
- Microsoft Windows 10 (1507, 1607, 1809, 21H2, 22H2) and Windows 11 (22H2, 23H2, 24H2)
- Microsoft Windows Server 2008, 2008 R2, 2012, 2012 R2, 2016, 2019, 2022, 2022 23H2
- Microsoft Windows Server 2025
Discovery Timeline
- 2024-11-12 - CVE-2024-43627 published to NVD
- 2024-11-12 - Microsoft releases security update for the Windows Telephony Service
- 2024-11-18 - Last updated in NVD database
Technical Details for CVE-2024-43627
Vulnerability Analysis
The vulnerability resides in the Windows Telephony Service (TAPI), a component that provides telephony Application Programming Interfaces (APIs) for applications interacting with telephony hardware and protocols. The issue is a heap-based buffer overflow [CWE-122] triggered when the service processes specially crafted input. An attacker who convinces a user to connect to or interact with a malicious server can trigger memory corruption inside the service. Once memory is corrupted, the attacker can hijack control flow and execute code in the service's security context. Because the attack vector is network-based and requires only user interaction, phishing and watering-hole delivery models are realistic exploitation paths.
Root Cause
The root cause is improper validation of data sizes prior to copying data into a heap-allocated buffer within the Telephony Service. This allows adjacent heap metadata and objects to be overwritten, enabling arbitrary code execution.
Attack Vector
A remote attacker hosts or controls a malicious endpoint and entices a user to initiate a telephony-related connection. The crafted response from the attacker overflows a heap buffer in the service, leading to code execution on the victim host without requiring valid credentials.
// No verified public proof-of-concept is available for CVE-2024-43627.
// See the Microsoft Security Response Center advisory for technical details.
Detection Methods for CVE-2024-43627
Indicators of Compromise
- Unexpected child processes spawned by svchost.exe hosting the Telephony Service (TapiSrv).
- Crash events or Windows Error Reporting entries referencing tapisrv.dll or related telephony modules.
- Outbound connections from telephony-related processes to untrusted external hosts.
Detection Strategies
- Monitor for anomalous behavior of the TapiSrv service, including memory access violations and unusual loaded modules.
- Hunt for process trees where svchost.exe -k NetworkService launches command interpreters such as cmd.exe or powershell.exe.
- Correlate user interaction events (link clicks, document opens) with subsequent telephony service activity.
Monitoring Recommendations
- Enable Windows Event Log forwarding for Service Control Manager, Application Error, and Sysmon process creation events.
- Track patch deployment status for the November 2024 Microsoft security update across all Windows endpoints and servers.
- Alert on network connections initiated by telephony components to non-corporate destinations.
How to Mitigate CVE-2024-43627
Immediate Actions Required
- Apply the Microsoft November 2024 security updates that address CVE-2024-43627 across all affected Windows and Windows Server systems.
- Prioritize patching of internet-facing and high-value servers, followed by user endpoints.
- Audit firewall and segmentation rules to restrict inbound telephony traffic from untrusted networks.
Patch Information
Microsoft issued cumulative updates addressing this vulnerability on November 12, 2024. Refer to the Microsoft Security Update Guide for CVE-2024-43627 for the specific KB articles applicable to each Windows build.
Workarounds
- Where patching cannot be applied immediately, disable the Telephony Service (TapiSrv) on systems that do not require telephony functionality.
- Block outbound and inbound telephony-related traffic at network perimeters and host-based firewalls.
- Enforce user awareness training to reduce the likelihood of users interacting with attacker-controlled telephony endpoints.
# Disable the Windows Telephony Service on hosts that do not require it
sc.exe config TapiSrv start= disabled
sc.exe stop TapiSrv
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
