CVE-2004-0820 in WinAmp
Summary
by MITRE
Winamp before 5.0.4 allows remote attackers to execute arbitrary script in the Local computer zone via script in HTML files that are referenced from XML files contained in a .wsz skin file.
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Analysis
by VulDB Data Team • 10/11/2025
The vulnerability described in CVE-2004-0820 represents a critical security flaw in Winamp media player versions prior to 5.0.4 that enables remote code execution through a sophisticated cross-site scripting attack vector. This vulnerability operates through a complex attack chain that leverages the trust relationship between the application and local resources, creating a dangerous privilege escalation scenario that was particularly severe in the context of media player software architecture.
The technical flaw manifests through Winamp's handling of .wsz skin files, which are XML-based configuration packages that can contain embedded HTML content. When a user opens a maliciously crafted .wsz file, the application processes the embedded XML structure and subsequently loads HTML content that references external script files. This processing occurs within the Local computer zone context, which grants the loaded scripts elevated privileges typically reserved for local applications. The vulnerability stems from inadequate input validation and sanitization of XML content within skin files, allowing attackers to inject malicious script code that executes with the privileges of the local user.
The operational impact of this vulnerability extends beyond simple remote code execution, as it creates a persistent threat vector that can be exploited through various delivery mechanisms. Attackers can craft malicious .wsz skin files that appear legitimate, potentially distributing them through compromised websites, peer-to-peer networks, or social engineering campaigns. Once executed, the malicious scripts can perform actions such as file system manipulation, registry modification, network communication, and privilege escalation. The Local computer zone execution context is particularly dangerous because it bypasses typical browser security restrictions that would normally prevent script execution from local resources.
This vulnerability aligns with CWE-74 and CWE-79 categories, which address injection flaws and cross-site scripting vulnerabilities respectively, while also mapping to several ATT&CK techniques including T1059 for command and script injection and T1068 for exploit for privilege escalation. The attack chain demonstrates how seemingly benign file format processing can be weaponized through improper trust model implementation. The vulnerability highlights the critical importance of secure input validation in applications that process user-supplied data, particularly when that data is interpreted in privileged contexts. Organizations should implement strict file format validation, sandboxing mechanisms, and regular security updates to prevent exploitation of similar vulnerabilities in media player software and other applications that handle user-provided configuration files.
The remediation approach for this vulnerability required comprehensive updates to Winamp's XML parser and skin file processing logic, implementing strict validation of embedded HTML content and enforcing proper security boundaries between different execution contexts. Security practitioners should emphasize the importance of principle of least privilege in application design, ensuring that user-supplied content never executes with elevated privileges. This vulnerability serves as a classic example of how trust relationships within applications can be exploited to create persistent security risks that require both application-level fixes and user education to fully mitigate.