CVE-2024-43628 Overview
CVE-2024-43628 is a remote code execution vulnerability in the Windows Telephony Service. Microsoft published the advisory on November 12, 2024 as part of its monthly security update cycle. The flaw is rooted in an integer overflow condition [CWE-190] within the Telephony Service component shipped across supported Windows client and server releases.
An unauthenticated network-based attacker can trigger the vulnerability when a user interacts with a crafted request, leading to code execution in the context of the Telephony Service. Successful exploitation impacts the confidentiality, integrity, and availability of the affected host.
Critical Impact
Remote attackers can execute arbitrary code on Windows endpoints and servers running the Telephony Service, enabling lateral movement and full host compromise after limited user interaction.
Affected Products
- Microsoft Windows 10 (versions 1507, 1607, 1809, 21H2, 22H2) across x86, x64, and ARM64
- Microsoft Windows 11 (versions 22H2, 23H2, 24H2) across x64 and ARM64
- Microsoft Windows Server 2008, 2012, 2016, 2019, 2022, 2022 23H2, and 2025
Discovery Timeline
- 2024-11-12 - CVE-2024-43628 published to the National Vulnerability Database
- 2024-11-12 - Microsoft released the security update addressing the vulnerability
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2024-43628
Vulnerability Analysis
The Windows Telephony Service (TapiSrv) exposes Telephony Application Programming Interface (TAPI) functionality used by communications applications. CVE-2024-43628 stems from an integer overflow [CWE-190] in the way the service processes attacker-influenced input. When an arithmetic operation on a size or length field wraps around the integer boundary, downstream memory operations use an undersized allocation or miscalculated offset.
The miscalculation results in memory corruption that an attacker can shape into arbitrary code execution within the Telephony Service process. The advisory classifies the attack vector as network with low complexity and no required privileges, but it requires user interaction to complete the exploit chain.
Root Cause
The root cause is an unchecked integer arithmetic operation on a length or count value derived from attacker-controlled input. The overflow produces a value smaller than the data subsequently copied or referenced, breaking the safety assumptions of later allocation and bounds checks. This pattern is consistent with [CWE-190: Integer Overflow or Wraparound].
Attack Vector
An attacker reaches the vulnerable code path over the network and induces a user to perform an action that causes the client to process a malicious Telephony-related request. The Telephony Service then performs the flawed arithmetic on the crafted input, triggering the overflow and memory corruption. Refer to the Microsoft Security Response Center advisory for the authoritative description. No public proof-of-concept code is available at this time.
Detection Methods for CVE-2024-43628
Indicators of Compromise
- Unexpected crashes or restarts of the TapiSrv service or the hosting svchost.exe instance running Telephony.
- Child processes spawned from the Telephony Service host that do not match historical baselines, such as command interpreters or scripting engines.
- Outbound network connections initiated by the Telephony Service host process to untrusted destinations.
Detection Strategies
- Monitor Windows Error Reporting and crash dumps for faults in modules associated with Telephony Service (tapisrv.dll, tapi32.dll).
- Alert on process creation events where the parent is the svchost.exe hosting Telephony and the child is an unusual binary.
- Correlate authentication, RPC, and process telemetry to identify network-sourced interactions immediately preceding Telephony Service anomalies.
Monitoring Recommendations
- Enable Sysmon process creation, image load, and network connection logging on systems where the Telephony Service is enabled.
- Track patch state for the November 2024 cumulative updates across all Windows clients and servers using vulnerability management tooling.
- Forward endpoint telemetry to a centralized analytics platform to detect lateral movement following any Telephony Service anomaly.
How to Mitigate CVE-2024-43628
Immediate Actions Required
- Apply the November 2024 Microsoft security updates that address CVE-2024-43628 to all affected Windows clients and servers.
- Inventory hosts where the Telephony Service is running or set to start automatically and prioritize patching for internet-exposed or high-value systems.
- Restrict inbound network access to systems with the Telephony Service enabled using host-based and perimeter firewall rules.
Patch Information
Microsoft published the patch alongside the CVE record on November 12, 2024. Administrators should consult the Microsoft CVE-2024-43628 Update guidance for the specific KB articles applicable to each operating system version and install the corresponding cumulative update.
Workarounds
- Disable the Telephony Service (TapiSrv) on systems that do not require TAPI functionality, after confirming no dependent applications are in use.
- Block inbound RPC traffic from untrusted networks at perimeter and host firewalls to limit reachability of the Telephony Service.
- Apply network segmentation so that endpoints exposing the Telephony Service are not directly reachable from user or guest network segments.
# Configuration example: disable the Windows Telephony Service where not required
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.
