CVE-2008-1734 in PHP Toolkit
Summary
by MITRE
Interpretation conflict in PHP Toolkit before 1.0.1 on Gentoo Linux might allow local users to cause a denial of service (PHP outage) and read contents of PHP scripts by creating a file with a one-letter lowercase alphabetic name, which triggers interpretation of a certain unquoted [a-z] argument as a matching shell glob for this name, rather than interpretation as the literal [a-z] regular-expression string, and consequently blocks the launch of the PHP interpreter within the Apache HTTP Server.
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Analysis
by VulDB Data Team • 08/09/2019
This vulnerability exists in the PHP Toolkit version 1.0.0 and earlier on Gentoo Linux systems, representing a critical interpretation conflict that can lead to both denial of service and information disclosure. The flaw stems from improper handling of shell argument interpretation when processing files with specific naming conventions, creating a dangerous condition that affects the Apache HTTP Server's ability to execute PHP scripts properly. The vulnerability specifically occurs when a local attacker creates a file with a single lowercase alphabetic character name, which then triggers unexpected shell globbing behavior during PHP processing.
The technical mechanism behind this vulnerability involves a critical flaw in argument parsing where unquoted shell arguments containing the pattern [a-z] are interpreted as shell glob patterns rather than literal regular expression strings. This misinterpretation causes the shell to expand the [a-z] pattern to match all lowercase letters in the current directory, effectively creating a conflict that prevents the PHP interpreter from launching correctly. The vulnerability manifests as a denial of service condition because the Apache server cannot properly execute PHP scripts, resulting in PHP outages that disrupt web application functionality. Additionally, the improper argument handling creates information disclosure risks as the system's file structure becomes accessible through the globbing behavior, potentially exposing sensitive PHP script contents to unauthorized users.
This vulnerability aligns with CWE-15 (External Control of System or Daemon) and CWE-78 (Improper Neutralization of Special Elements used in an OS Command) categories, demonstrating how improper shell argument handling can create both execution and information disclosure risks. The ATT&CK framework categorizes this under T1059 (Command and Scripting Interpreter) and T1190 (Exploit Public-Facing Application) as it leverages shell command injection techniques to compromise system availability and confidentiality. The local privilege escalation aspect is particularly concerning as it allows attackers with minimal access to create files that can severely impact system operations, potentially affecting multiple web applications hosted on the same server.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be exploited to gain unauthorized access to PHP script contents and potentially compromise the entire web application infrastructure. Attackers can systematically create files with single lowercase letters to test for this vulnerability, and once confirmed, they can maintain persistent access to sensitive application data. The vulnerability affects systems where PHP is executed through Apache, making it particularly dangerous for web hosting environments and applications that rely on PHP processing. Mitigation strategies must include updating to PHP Toolkit version 1.0.1 or later, implementing proper input validation for file naming conventions, and ensuring that shell arguments are properly quoted to prevent glob expansion. System administrators should also consider implementing file access controls and monitoring for unusual file creation patterns that might indicate exploitation attempts.
The vulnerability demonstrates the importance of proper shell argument handling in security-critical applications and highlights how seemingly minor implementation flaws can create significant security risks. Organizations running affected systems should immediately apply the available patches and conduct thorough security assessments to identify potential exploitation attempts. Additional defensive measures include implementing proper file system permissions, monitoring for unauthorized file creation, and ensuring that all system components properly sanitize inputs to prevent shell injection attacks. The incident underscores the need for comprehensive security testing of system integration points and proper validation of all external inputs in web application environments to prevent similar interpretation conflicts from occurring in other components.