CVE-2015-5624 in ELPhoneBtnV6 ActiveX Control
Summary
by MITRE
Buffer overflow in the ExecCall method in c2lv6.ocx in the FreeBit ELPhoneBtnV6 ActiveX control allows remote attackers to execute arbitrary code via a crafted HTML document, related to the discontinued "Click to Live" service.
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Analysis
by VulDB Data Team • 12/01/2017
The CVE-2015-5624 vulnerability represents a critical buffer overflow flaw within the FreeBit ELPhoneBtnV6 ActiveX control, specifically in the ExecCall method of the c2lv6.ocx component. This vulnerability emerged from the discontinued "Click to Live" service and poses significant security risks due to its remote exploitation capabilities. The ActiveX control was designed to facilitate telephony functionality within web browsers, but the implementation contained a fundamental flaw that allowed attackers to manipulate memory structures through maliciously crafted HTML documents.
The technical flaw manifests as a classic buffer overflow condition where the ExecCall method fails to properly validate input parameters before copying data into fixed-size buffers. This oversight enables attackers to overflow the allocated memory space and potentially overwrite adjacent memory locations, including return addresses and function pointers. The vulnerability specifically affects systems running Windows operating systems with the FreeBit ELPhoneBtnV6 ActiveX control installed, creating an attack surface where remote code execution becomes possible through web-based exploitation. The flaw stems from inadequate bounds checking and memory management practices within the ActiveX component's implementation.
The operational impact of this vulnerability extends beyond simple remote code execution, as it provides attackers with complete system compromise capabilities. Successful exploitation allows malicious actors to execute arbitrary code with the privileges of the user running the vulnerable ActiveX control, typically resulting in full system compromise. The vulnerability's remote nature means that attackers can leverage this flaw through web browsers without requiring local system access, making it particularly dangerous in enterprise environments where users may browse untrusted websites. This threat vector aligns with ATT&CK technique T1190 for exploitation of remote services and T1059 for command and script interpreter usage, representing a comprehensive attack chain that can lead to persistent system compromise.
Mitigation strategies for CVE-2015-5624 primarily focus on eliminating the vulnerable ActiveX control from affected systems, as the component is discontinued and no official patches exist for the vulnerability. Organizations should implement browser security policies that disable ActiveX controls or restrict their execution to trusted sites only. The remediation process involves removing the c2lv6.ocx file from system directories and updating registry entries that reference the vulnerable component. Additionally, network administrators should consider implementing web application firewalls and content filtering solutions to prevent access to known malicious websites that may exploit this vulnerability. This case demonstrates the ongoing security risks associated with legacy ActiveX controls and highlights the importance of maintaining up-to-date security practices to address deprecated software components. The vulnerability serves as a prime example of how discontinued software products can create persistent security risks that require proactive removal rather than patching approaches. Organizations should conduct comprehensive asset inventories to identify all instances of this ActiveX control and ensure complete removal to prevent exploitation attempts.