CVE-2002-0223 in WWWThreads
Summary
by MITRE
Infopop UBB.Threads 5.4 and Wired Community Software WWWThreads 5.0 through 5.0.9 allows remote attackers to upload arbitrary files by using a filename that contains an accepted extension, but ends in a different extension.
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Analysis
by VulDB Data Team • 09/21/2025
The vulnerability described in CVE-2002-0223 represents a critical file upload security flaw affecting Infopop UBB.Threads 5.4 and Wired Community Software WWWThreads versions 5.0 through 5.0.9. This issue stems from inadequate input validation mechanisms within the file upload functionality, creating a path for remote attackers to bypass security restrictions through clever manipulation of filename extensions. The vulnerability operates by exploiting the way these applications process and validate file extensions during upload operations, allowing malicious actors to circumvent intended security controls.
The technical flaw manifests when the application performs file extension validation using a method that only checks the final portion of a filename without proper sanitization of the entire filename string. Attackers can exploit this by crafting filenames that contain legitimate extensions such as .jpg or .gif followed by additional extensions that are not properly filtered. For instance, a filename like exploit.jpg.php could be accepted by the vulnerable system, where the system recognizes .jpg as an acceptable extension but fails to properly validate the complete filename structure. This approach leverages the principle of insecure file upload validation and represents a classic example of improper input sanitization that falls under CWE-434.
The operational impact of this vulnerability is severe as it allows attackers to upload malicious files such as web shells, script files, or other harmful content that can be executed on the target server. Once uploaded, these files can provide attackers with persistent access to the system, enabling them to execute arbitrary commands, steal sensitive data, or use the compromised server as a launch point for further attacks. The vulnerability creates a direct path for privilege escalation and persistent access, making it particularly dangerous for web applications hosting user-generated content or forums where file uploads are permitted. This type of vulnerability directly maps to attack techniques described in the MITRE ATT&CK framework under the T1190 category for Exploit Public-Facing Application, and specifically relates to T1059 for Command and Scripting Interpreter.
Mitigation strategies for CVE-2002-0223 require immediate implementation of proper file validation mechanisms that examine the complete filename and content rather than relying solely on extension checks. Organizations should implement a whitelist approach for acceptable file types, validate file content using magic number detection, and ensure that uploaded files are stored in non-executable directories. Additionally, proper input sanitization and encoding of filenames should be implemented to prevent the exploitation of path traversal and extension manipulation techniques. The fix should also include implementing proper file type detection mechanisms that examine actual file content rather than relying on extension-based validation, which aligns with security best practices outlined in OWASP Top Ten and other industry standards for secure file upload implementations.