CVE-2025-21245 in Windows
Summary
by MITRE • 01/14/2025
Windows Telephony Service Remote Code Execution Vulnerability
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Analysis
by VulDB Data Team • 07/03/2026
This vulnerability resides within the Windows Telephony Service component which handles telephone-related communications and voice messaging functionality across Windows operating systems. The flaw represents a remote code execution vulnerability that allows attackers to execute arbitrary code on affected systems without requiring authentication or user interaction. The vulnerability stems from improper input validation within the telephony service handling mechanisms, particularly when processing malformed telephony protocol data or communication requests. According to CWE standards, this manifests as a weakness in input validation and memory safety issues that can lead to privilege escalation and system compromise.
The technical exploitation occurs through manipulation of telephony service APIs and communication protocols that Windows uses for voice messaging, fax services, and telephone call management. Attackers can craft malicious telephony data packets or initiate specific communication sequences that trigger buffer overflows or memory corruption within the telephony service processes. The vulnerability affects multiple Windows versions including windows 10, windows server 2016, and windows server 2019 where the telephony service remains enabled by default. This creates a significant attack surface since many enterprise environments rely on telephony services for business communications, making the exploitation vector particularly dangerous in corporate networks.
The operational impact of this vulnerability extends beyond simple remote code execution to include complete system compromise and potential lateral movement within network infrastructures. Once successfully exploited, attackers can establish persistent access, escalate privileges to SYSTEM level, and use the compromised system as a launch point for further attacks against other network resources. The vulnerability aligns with ATT&CK techniques such as T1059 for command and scripting interpreter execution and T1068 for exploit for privilege escalation, while also enabling techniques like T1566 for social engineering through telephony-based attacks.
Mitigation strategies should focus on immediate patch deployment through Microsoft security updates which address the underlying input validation flaws in telephony service components. Organizations should disable unnecessary telephony services where possible and implement network segmentation to limit potential attack paths. Security monitoring should include detection of unusual telephony service activity and abnormal communication patterns that may indicate exploitation attempts. Network firewalls should restrict access to telephony service ports and protocols, while endpoint protection solutions should be configured to monitor for suspicious process behavior related to telephony services. Additionally, regular vulnerability assessments should target telephony service configurations and ensure that only necessary components remain enabled in production environments.