CVE-2004-1114 in Skype
Summary
by MITRE
Buffer overflow in the handling of command line arguments in Skype 1.0.x.94 through 1.0.x.98 allows remote attackers to execute arbitrary code via a callto:// URL with a long non-existent username, a different vulnerability than CVE-2004-1777.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 06/11/2019
The vulnerability described in CVE-2004-1114 represents a critical buffer overflow flaw within Skype version 1.0.x.94 through 1.0.x.98 that specifically targets the application's command line argument handling mechanism. This issue arises when Skype processes callto:// URLs that contain excessively long non-existent usernames, creating a scenario where memory boundaries are exceeded during string processing operations. The flaw demonstrates characteristics consistent with CWE-121, which describes stack-based buffer overflow conditions where insufficient bounds checking allows attackers to overwrite adjacent memory locations. The vulnerability operates through the application's URL protocol handler, which is designed to process external calls and establish connections within the communication framework.
The technical implementation of this vulnerability exploits the lack of proper input validation within Skype's argument parsing subsystem. When a maliciously crafted callto:// URL is processed, the application fails to properly validate the length of the username parameter, allowing an attacker to provide an argument that exceeds the allocated buffer space. This overflow can potentially overwrite critical memory segments including return addresses, function pointers, or other control data structures. The attack vector leverages the fact that Skype's protocol handler does not implement adequate bounds checking or input sanitization before processing user-supplied data, making it susceptible to exploitation through external URL invocation mechanisms. The vulnerability differs from CVE-2004-1777 in that it specifically targets command line argument processing rather than other attack surfaces, though both vulnerabilities share the common theme of insufficient input validation in Skype's communication protocols.
The operational impact of this vulnerability extends beyond simple code execution, as successful exploitation can provide attackers with complete control over the affected system. Remote attackers can leverage this buffer overflow to inject and execute arbitrary code with the privileges of the Skype process, potentially leading to system compromise, data theft, or further network infiltration. The attack requires only the ability to deliver a malicious URL to a victim who has Skype installed, making it particularly dangerous in environments where users frequently interact with external web content or email attachments. The vulnerability affects systems where Skype is installed and actively processes external calls, with the attack surface expanding to include any user who might encounter the malicious URL in normal usage patterns. This makes the vulnerability particularly concerning for enterprise environments where Skype is widely deployed.
Mitigation strategies for CVE-2004-1114 should prioritize immediate remediation through official software updates from Skype, as the vulnerability was addressed in subsequent releases of the application. Organizations should implement network-level controls to block or filter callto:// URL protocols at perimeter defenses, reducing the attack surface for potential exploitation attempts. Additionally, user education programs should emphasize the dangers of clicking unknown URLs, particularly those containing callto:// protocols that might trigger the vulnerable code path. System administrators should consider implementing application whitelisting policies that restrict execution of Skype unless explicitly authorized, along with monitoring for suspicious process execution patterns that might indicate exploitation attempts. The vulnerability serves as a prime example of why proper input validation and bounds checking should be implemented as fundamental security measures in all application development processes, aligning with ATT&CK technique T1059.007 for command and scripting interpreter usage, where the overflow could be leveraged to execute malicious commands through the compromised Skype process.