CVE-2004-1777 in Skype
Summary
by MITRE
A "range check error" in Skype for Windows before 0.98.0.28 allows local and remote attackers to cause a denial of service (application crash) via long command line arguments or a long callto:// URL, a different vulnerability than CVE-2004-1114.
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Analysis
by VulDB Data Team • 06/15/2019
The vulnerability identified as CVE-2004-1777 represents a critical range check error in Skype for Windows versions prior to 0.98.0.28 that fundamentally undermines the application's stability and security posture. This flaw manifests as a buffer over-read condition that occurs when the application processes command line arguments or callto URLs exceeding normal parameter lengths. The vulnerability exists within the Skype client's input validation mechanisms, specifically in how it handles user-supplied data during the parsing of these particular URI formats.
The technical implementation of this vulnerability stems from inadequate bounds checking in the application's argument processing routines. When Skype encounters command line arguments or callto:// URLs that exceed predetermined length thresholds, the application fails to properly validate the input boundaries before attempting to process the data. This results in the program attempting to read memory locations beyond the allocated buffer space, causing unpredictable behavior including application crashes and potential system instability. The vulnerability operates at the application layer and can be exploited through both local and remote attack vectors, making it particularly dangerous in networked environments.
From an operational impact perspective, this vulnerability creates significant risk for users and organizations relying on Skype for Windows as their primary communication platform. The denial of service condition can be triggered by simply providing malformed command line parameters or specially crafted callto:// URLs, requiring no specialized knowledge or privileged access. Attackers can leverage this weakness to disrupt communication services, potentially causing business continuity issues in enterprise environments where Skype is extensively used for voice and video conferencing. The vulnerability's remote exploitability means that malicious actors can trigger the denial of service condition through network-based attacks without requiring physical access to target systems.
The flaw aligns with CWE-129, which specifically addresses improper validation of length of input buffers, and demonstrates characteristics consistent with ATT&CK technique T1499.004 for network denial of service attacks. Organizations should implement immediate mitigation strategies including updating to Skype version 0.98.0.28 or later, which contains the necessary patches to address the range check error. Network administrators should also consider implementing input validation controls at network boundaries to filter out suspicious command line arguments and URL formats. Additionally, users should be educated about the risks of executing unknown command line parameters and should avoid clicking on untrusted callto:// links that could trigger this vulnerability. The remediation process requires careful attention to ensure that all instances of the vulnerable Skype client are updated across the organization, as partial deployment can leave systems vulnerable to exploitation.