CVE-2003-0275 in YaBB
Summary
by MITRE
SSI.php in YaBB SE 1.5.2 allows remote attackers to execute arbitrary PHP code by modifying the sourcedir parameter to reference a URL on a remote web server that contains the code.
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Analysis
by VulDB Data Team • 08/21/2025
The vulnerability described in CVE-2003-0275 represents a critical server-side inclusion flaw within the YaBB SE 1.5.2 bulletin board system. This issue stems from improper input validation and sanitization mechanisms that fail to properly restrict user-controllable parameters, specifically the sourcedir parameter within the SSI.php script. The vulnerability creates an environment where remote attackers can manipulate the application's behavior by injecting malicious URLs into the parameter, effectively bypassing normal security boundaries. This flaw operates at the intersection of insecure input handling and remote code execution capabilities, making it particularly dangerous for web applications that process user-supplied data without adequate validation.
The technical exploitation of this vulnerability occurs through a classic server-side include attack vector where the sourcedir parameter is manipulated to reference external web resources. When the SSI.php script processes this parameter, it fails to validate or sanitize the input, allowing it to directly include and execute code from remote servers. This type of vulnerability aligns with CWE-98, which describes improper restriction of operations within a recognized security scope, and CWE-20, which covers improper input validation. The attack leverages the application's trust in user-provided data without sufficient verification, creating a pathway for arbitrary code execution that can compromise the entire web server environment.
The operational impact of this vulnerability extends far beyond simple data theft or disruption. Successful exploitation allows attackers to execute arbitrary PHP code with the privileges of the web server process, potentially enabling complete system compromise. Attackers can leverage this vulnerability to upload malicious files, establish backdoors, access sensitive data, or use the compromised server as a launch point for further attacks against internal networks. The vulnerability's remote nature means that attackers do not require local system access or credentials, making it particularly attractive for automated exploitation campaigns. This aligns with ATT&CK technique T1190, which describes exploitation of remote services, and demonstrates how insecure parameter handling can create persistent security weaknesses in web applications.
Mitigation strategies for this vulnerability must address both the immediate exposure and underlying architectural issues. The most effective immediate solution involves implementing strict input validation and sanitization for all user-controllable parameters, particularly those used in file inclusion operations. Organizations should implement whitelisting mechanisms that restrict the sourcedir parameter to only accept predefined, trusted directories or URLs. Additionally, the application should be configured to disable remote file inclusion capabilities entirely, using PHP configuration settings such as allow_url_include = Off. Regular security updates and patches should be implemented immediately, as this vulnerability existed in a specific version of YaBB SE and was likely addressed in subsequent releases. Network-level protections such as web application firewalls can also provide additional defense-in-depth measures to detect and block exploitation attempts targeting this specific vulnerability pattern.