CVE-2007-4652 in PHP
Summary
by MITRE
The session extension in PHP before 5.2.4 might allow local users to bypass open_basedir restrictions via a session file that is a symlink.
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Analysis
by VulDB Data Team • 04/13/2025
The vulnerability described in CVE-2007-4652 represents a critical security flaw in PHP's session handling mechanism that could potentially allow local attackers to circumvent important security restrictions. This issue specifically affects PHP versions prior to 5.2.4 and exploits weaknesses in how the system manages session files when symbolic links are involved. The vulnerability stems from improper validation of session file paths, creating a potential attack vector that could be leveraged by malicious users with local access to the system. The security implications extend beyond simple privilege escalation, as this flaw could enable attackers to access files and directories that should normally be restricted by the open_basedir configuration.
The technical root cause of this vulnerability lies in PHP's session extension's handling of symbolic links within session file paths. When PHP creates or accesses session files, it does not properly resolve symbolic links to their actual target locations before applying open_basedir restrictions. This means that if an attacker can manipulate the session file to be a symbolic link pointing to a restricted directory, the system will incorrectly validate the session file's location based on the symbolic link's path rather than the actual target path. The flaw creates a path traversal scenario where the security boundaries established by open_basedir can be bypassed through careful manipulation of file system links. This type of vulnerability is classified under CWE-22 as Path Traversal and aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter.
The operational impact of this vulnerability is significant for any system running affected PHP versions, particularly those that rely on open_basedir for security isolation. Local users who can create or manipulate session files can exploit this weakness to access restricted directories and potentially read sensitive files that should be protected by the open_basedir configuration. This could lead to information disclosure, privilege escalation, and unauthorized access to system resources that are normally protected by PHP's security mechanisms. The vulnerability is particularly dangerous in shared hosting environments or multi-tenant systems where proper isolation between different user accounts is critical for maintaining security boundaries. Attackers could leverage this flaw to access configuration files, database credentials, or other sensitive data that should be restricted to specific users or processes.
System administrators and security professionals should prioritize patching affected PHP installations to mitigate this vulnerability, as the fix in PHP 5.2.4 properly addresses the symbolic link resolution issue in session handling. The recommended mitigation strategy includes updating PHP to version 5.2.4 or later, implementing proper file system permissions to prevent unauthorized symlink creation, and monitoring session file creation patterns for suspicious activity. Organizations should also review their open_basedir configurations to ensure they are properly enforced and consider implementing additional security controls such as file integrity monitoring and access logging for session files. This vulnerability demonstrates the importance of proper input validation and path resolution in security-critical applications, particularly in environments where file system access controls are essential for maintaining system integrity. The issue also highlights the need for comprehensive security testing of application components that handle file system operations, including symbolic link handling and path validation mechanisms.