CVE-2003-1373 in phpBB
Summary
by MITRE
Directory traversal vulnerability in auth.php for PhpBB 1.4.0 through 1.4.4 allows remote attackers to read and include arbitrary files via .. (dot dot) sequences followed by NULL (%00) characters in CGI parameters, as demonstrated using the lang parameter in prefs.php.
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Analysis
by VulDB Data Team • 06/16/2018
The vulnerability described in CVE-2003-1373 represents a critical directory traversal flaw affecting PhpBB versions 1.4.0 through 1.4.4. This security weakness stems from inadequate input validation within the authentication and language selection mechanisms of the bulletin board system. The flaw specifically manifests when the application processes CGI parameters containing directory traversal sequences followed by null byte characters, creating a pathway for unauthorized file access and potential code execution. The vulnerability is particularly dangerous because it allows attackers to bypass normal access controls and directly access sensitive system files that should remain protected from user interaction.
The technical implementation of this vulnerability leverages the combination of directory traversal sequences and null byte encoding to manipulate how the application processes file paths. When the lang parameter in prefs.php receives input containing .. (dot dot) sequences followed by %00 characters, the application fails to properly sanitize these inputs before using them in file operations. This improper input handling creates a condition where the application interprets the malicious input as a legitimate file path specification, allowing attackers to navigate to arbitrary directories within the file system. The null byte injection technique is particularly effective because it can terminate string processing in the application layer, enabling attackers to bypass certain security checks that might otherwise prevent access to protected files.
The operational impact of this vulnerability extends beyond simple information disclosure to potentially enable full system compromise. Attackers can leverage this flaw to read sensitive configuration files, database credentials, user authentication data, and other critical system files that may contain passwords, API keys, or other confidential information. The vulnerability also opens possibilities for remote code execution if the application includes functionality that processes user-supplied data in a way that allows code inclusion from arbitrary locations. This represents a severe threat to web application security as it allows attackers to gain unauthorized access to system resources that should remain isolated from public access.
Security professionals should implement multiple layers of mitigation to address this vulnerability effectively. The primary solution involves immediate patching of affected PhpBB installations to versions that properly validate and sanitize input parameters. Additionally, web application firewalls should be configured to detect and block requests containing suspicious directory traversal sequences and null byte encodings. Input validation should be strengthened at multiple levels including application code, web server configuration, and network security controls. Organizations should also conduct comprehensive security assessments to identify other potential directory traversal vulnerabilities within their web applications and ensure proper access controls are implemented. This vulnerability aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, and represents a classic example of how inadequate input validation can lead to severe security consequences. The attack pattern described in the vulnerability follows common ATT&CK techniques for privilege escalation and information gathering through path traversal methods.