CVE-2005-0056 in Internet Explorer
Summary
by MITRE
Internet Explorer 5.01, 5.5, and 6 does not properly validate certain URLs in Channel Definition Format (CDF) files, which allows remote attackers to obtain sensitive information or execute arbitrary code, aka the "Channel Definition Format (CDF) Cross Domain Vulnerability."
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 07/05/2025
The vulnerability identified as CVE-2005-0056 represents a critical security flaw in Microsoft Internet Explorer versions 5.01, 5.5, and 6.0 that stems from improper validation of URLs within Channel Definition Format files. This issue falls under the category of cross-domain security vulnerabilities and specifically targets the way Internet Explorer processes CDF files that define channels for content aggregation. The flaw allows attackers to exploit the browser's handling of these files to either extract sensitive information from the system or execute arbitrary code with the privileges of the logged-in user. The vulnerability is particularly dangerous because it leverages the trust model that Internet Explorer establishes between different domains, creating a pathway for malicious actors to bypass security boundaries that should normally protect users from unauthorized access to system resources.
The technical implementation of this vulnerability occurs when Internet Explorer encounters a CDF file that contains specially crafted URLs that are not properly validated by the browser's security mechanisms. CDF files are designed to allow users to subscribe to content feeds from various sources, but the validation process fails to adequately check the origins and destinations of these URLs. This weakness enables attackers to craft malicious CDF files that can redirect users to malicious websites or load content from unauthorized domains. The vulnerability specifically affects how Internet Explorer handles cross-domain requests within the context of CDF files, where the browser's security model does not sufficiently enforce domain restrictions. According to CWE-20, this represents a weakness in the design or implementation of input validation mechanisms, while the ATT&CK framework categorizes this under T1203 - Exploitation for Client Execution, as it allows for arbitrary code execution through browser-based attacks. The flaw essentially creates a trust boundary violation where the browser incorrectly processes URLs that should be restricted due to domain mismatch or security concerns.
The operational impact of this vulnerability extends beyond simple information disclosure to include complete system compromise potential. Attackers can leverage this vulnerability to execute malicious code remotely without requiring user interaction beyond visiting a malicious website or opening a compromised CDF file. The attack surface is particularly wide since CDF files can be distributed through various vectors including email attachments, web downloads, or malicious websites. Successful exploitation can result in unauthorized access to sensitive data, system file manipulation, registry modification, and potentially full system control. The vulnerability affects users across multiple Internet Explorer versions, making it particularly dangerous as it impacts a broad user base. Security researchers have noted that this vulnerability can be exploited in conjunction with other attack vectors to create more sophisticated attack chains, where the initial compromise through CDF files serves as a foothold for further exploitation. The vulnerability's impact is amplified by the fact that many users and organizations were still using these older versions of Internet Explorer during the time this vulnerability was active, creating a substantial attack surface.
Mitigation strategies for CVE-2005-0056 focus primarily on updating to patched versions of Internet Explorer or implementing administrative controls that prevent CDF file execution. Microsoft released security updates that addressed the validation issues in CDF file processing, and users should ensure they have installed the appropriate patches. Organizations should consider disabling CDF file support entirely in their browser configurations or implementing strict content filtering policies that prevent execution of potentially malicious CDF files. Network-level controls such as web application firewalls and content filtering systems can help detect and block malicious CDF files before they reach end users. Additionally, user education and awareness programs should emphasize the dangers of opening unknown or untrusted CDF files, as social engineering remains a common attack vector for exploiting this vulnerability. The ATT&CK framework suggests implementing process monitoring and behavioral analysis to detect anomalous execution patterns that might indicate exploitation attempts. Organizations should also consider implementing sandboxing techniques to isolate browser processes and limit the potential damage from successful exploitation attempts. According to industry best practices, this vulnerability highlights the importance of maintaining up-to-date software and implementing defense-in-depth strategies that protect against multiple attack vectors simultaneously.