CVE-2003-0332 in Badblue
Summary
by MITRE
The ISAPI extension in BadBlue 1.7 through 2.2, and possibly earlier versions, modifies the first two letters of a filename extension after performing a security check, which allows remote attackers to bypass authentication via a filename with a .ats extension instead of a .hts extension.
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Analysis
by VulDB Data Team • 08/18/2025
The vulnerability identified as CVE-2003-0332 represents a critical authentication bypass flaw within the ISAPI extension of BadBlue web server software versions 1.7 through 2.2, with potential prevalence in earlier releases. This security weakness stems from a specific implementation error in how the software handles filename extensions during authentication processes, creating a pathway for unauthorized access that directly undermines the security model of the affected system. The flaw operates through a manipulation of file extension handling that occurs after initial security validation checks have been completed.
The technical mechanism behind this vulnerability involves the ISAPI extension's improper modification of filename extensions by altering the first two characters of file extensions, specifically targeting the .hts extension format. When a user attempts to access protected resources, the system performs an initial security check using the .hts extension, but subsequent processing modifies this extension to .ats, effectively bypassing the authentication mechanisms that were designed to protect these resources. This behavior creates a window where attackers can exploit the system by simply changing the extension from .hts to .ats, thereby circumventing the intended access controls and gaining unauthorized access to protected content.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it represents a fundamental flaw in the authentication architecture that could enable attackers to bypass multiple security controls simultaneously. This type of vulnerability directly relates to CWE-284, which addresses improper access control mechanisms, and demonstrates how implementation-level errors in security validation can create systemic weaknesses. The vulnerability's exploitation does not require complex attack vectors or specialized tools, making it particularly dangerous as it can be readily exploited by attackers with basic knowledge of the system's behavior. The modification of filename extensions occurs at the ISAPI extension level, indicating that this is not merely a configuration issue but a core architectural flaw in the software's security implementation.
Security professionals should note that this vulnerability demonstrates the importance of proper input validation and authentication flow management within web server extensions. The attack pattern aligns with techniques described in the ATT&CK framework under privilege escalation and credential access tactics, where attackers manipulate system components to bypass authentication. The vulnerability's persistence across multiple versions of the software indicates that the underlying design flaw was not properly addressed in subsequent releases, highlighting the need for comprehensive security testing and validation of authentication mechanisms. Organizations using BadBlue software should immediately implement mitigations including disabling the affected ISAPI extension, implementing network-level access controls, and considering immediate software upgrades to versions that address this specific vulnerability. The flaw also underscores the necessity of thorough security reviews of third-party components and the importance of understanding how authentication mechanisms interact with file system operations in web server environments.
The vulnerability's classification as an authentication bypass flaw makes it particularly concerning for environments where sensitive data is stored and accessed through the affected software. The ease with which attackers can exploit this weakness through simple filename manipulation demonstrates how seemingly minor implementation details can create significant security risks. This type of vulnerability also serves as a reminder of the importance of defense in depth strategies, where multiple layers of security controls are implemented to prevent exploitation even when individual controls fail. Organizations should conduct comprehensive vulnerability assessments to identify similar implementation flaws in other software components and ensure that authentication mechanisms are properly validated and enforced throughout the system architecture.