CVE-2005-4426 in YaBB
Summary
by MITRE
Interpretation conflict in YaBB before 2.1 allows remote authenticated users to inject arbitrary web script or HTML via HTML in a file with a GIF file extension, which causes the HTML to be executed by a victim who views the file in Internet Explorer as a result of CVE-2005-3312. NOTE: it could be argued that this vulnerability is due to a design flaw in Internet Explorer and the proper fix should be in that browser; if so, then this should not be treated as a vulnerability in YaBB.
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Analysis
by VulDB Data Team • 07/15/2018
The vulnerability described in CVE-2005-4426 represents a sophisticated interpretation conflict within the YaBB bulletin board system prior to version 2.1, exploiting a fundamental design flaw in web browser handling of file extensions and content types. This security flaw arises from the improper validation and interpretation of file metadata, specifically when files with gif extensions contain embedded html content that gets executed in vulnerable browser environments. The vulnerability demonstrates how web applications can inadvertently create attack vectors through their file handling mechanisms, particularly when they fail to properly validate file content against declared extensions.
The technical exploitation of this vulnerability occurs through a specific attack pattern involving file extension manipulation and browser-specific rendering behaviors. An authenticated attacker with access to the YaBB system can upload a file with a .gif extension that actually contains html or javascript content. When victims view this file in Internet Explorer, the browser's handling of the gif extension combined with the embedded html content creates a scenario where the html gets executed as part of the page rendering process. This vulnerability directly leverages CVE-2005-3312, which specifically addresses Internet Explorer's handling of certain file types and extensions, creating a chain of exploitation that bypasses normal security boundaries.
From an operational perspective, this vulnerability presents a significant risk to users of YaBB systems, particularly in environments where users may not be security-aware and routinely click on attachments or images from untrusted sources. The attack requires only authenticated access to the bulletin board system, making it potentially exploitable by insiders or compromised accounts. The impact extends beyond simple script execution to potentially allow for session hijacking, data theft, or further exploitation of the victim's system through more sophisticated attacks that leverage the initial script injection. This vulnerability type falls under CWE-74 which describes improper neutralization of special elements in output used by a downstream component, and CWE-20 which covers improper input validation.
The mitigation strategies for this vulnerability involve multiple layers of defense, beginning with proper input validation and file type checking within the YaBB application itself. System administrators should implement strict file extension and content validation mechanisms that prevent html content from being stored with gif extensions, while also ensuring that the web server properly handles content type headers. Additionally, users should be educated about the risks of clicking on attachments from untrusted sources, and organizations should consider implementing web application firewalls that can detect and block suspicious file content patterns. The vulnerability highlights the importance of defense in depth approaches and proper separation of concerns in web application design, where the application should not rely on browser-specific behaviors for security enforcement. This issue also demonstrates the critical need for proper security testing that includes edge cases involving file type manipulation and browser compatibility issues, particularly when dealing with legacy web applications that may not have been designed with modern security practices in mind. The vulnerability's classification as potentially browser-specific raises important questions about shared responsibility in security and the need for comprehensive threat modeling that considers both application-level and browser-level security implications.