CVE-2002-0934 in Alienform2
Summary
by MITRE
Directory traversal vulnerability in Jon Hedley AlienForm2 (typically installed as af.cgi or alienform.cgi) allows remote attackers to read or modify arbitrary files via an illegal character in the middle of a .. (dot dot) sequence in the parameters (1) _browser_out or (2) _out_file.
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Analysis
by VulDB Data Team • 05/13/2019
The vulnerability identified as CVE-2002-0934 represents a critical directory traversal flaw within Jon Hedley AlienForm2 web application, commonly deployed as af.cgi or alienform.cgi scripts. This security weakness stems from inadequate input validation mechanisms that fail to properly sanitize user-supplied parameters containing directory traversal sequences. The vulnerability specifically affects two parameters named _browser_out and _out_file which are processed by the application to determine file output locations. When attackers insert illegal characters within the .. (dot dot) sequences used for directory navigation, the application fails to properly validate these inputs, allowing unauthorized access to arbitrary files on the server filesystem. This flaw operates at the application layer and can be exploited through web-based attacks targeting the vulnerable CGI script.
The technical implementation of this vulnerability aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal attacks. The flaw occurs because the application does not adequately filter or normalize input parameters before using them in file system operations. When the script processes parameters containing sequences like ../../../etc/passwd or similar traversal patterns with embedded illegal characters, the normalization logic fails to properly resolve these paths, resulting in the application attempting to access files outside its intended directory boundaries. This represents a classic case of insufficient input sanitization where the application trusts user input without proper validation or canonicalization of path references.
The operational impact of this vulnerability is severe and multifaceted, as it provides attackers with the capability to read or modify arbitrary files on the affected system. Successful exploitation could lead to complete system compromise, data theft, or unauthorized modification of critical application files. Attackers could potentially access sensitive configuration files, database credentials, user information, or system files that should remain protected. The vulnerability also aligns with ATT&CK technique T1083, which covers directory and file permissions enumeration, as attackers could use this flaw to discover and access files that would normally be restricted. Additionally, this vulnerability enables potential privilege escalation scenarios where attackers might access files with elevated permissions that are typically protected from regular user access, making it particularly dangerous in multi-user or shared hosting environments.
Mitigation strategies for CVE-2002-0934 should focus on immediate input validation and parameter sanitization measures. Organizations should implement strict input filtering that rejects or normalizes any input containing directory traversal sequences before processing. The recommended approach includes canonicalizing all file paths and ensuring that user-supplied parameters are validated against a whitelist of acceptable values. Additionally, implementing proper file access controls and restricting the web application's ability to access sensitive system directories is crucial. The vulnerability also highlights the importance of keeping legacy applications updated, as AlienForm2 represents an older web application that may contain multiple unpatched security issues. System administrators should consider removing or replacing vulnerable CGI scripts entirely, as the original application is no longer maintained and likely contains additional undiscovered vulnerabilities. Network segmentation and web application firewalls can provide additional layers of protection, though these should not be considered substitutes for proper input validation and secure coding practices that address the root cause of the vulnerability.