CVE-2007-4663 in PHP
Summary
by MITRE
Directory traversal vulnerability in PHP before 5.2.4 allows attackers to bypass open_basedir restrictions via unspecified vectors involving the glob function.
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Analysis
by VulDB Data Team • 09/07/2018
The directory traversal vulnerability identified as CVE-2007-4663 represents a critical security flaw in PHP versions prior to 5.2.4 that specifically targets the open_basedir restriction mechanism. This vulnerability allows malicious actors to circumvent PHP's security controls that are designed to limit file access within specific directories, thereby enabling unauthorized access to files and directories outside the intended scope. The flaw manifests through unspecified vectors that involve the glob function, which is commonly used for pattern matching and file system operations in PHP applications. The open_basedir directive serves as a crucial security boundary in PHP environments, restricting file access to specific directories and preventing attackers from reading arbitrary files on the server. When this restriction is bypassed through the glob function vulnerability, it creates a pathway for attackers to potentially access sensitive system files, configuration data, or other restricted resources that should remain protected from unauthorized access.
The technical implementation of this vulnerability exploits the interaction between the glob function and PHP's path resolution mechanisms. The glob function in PHP is designed to find pathnames matching a specified pattern, but in vulnerable versions, it fails to properly validate or sanitize input parameters when processing directory traversal sequences. This allows attackers to craft malicious input that includes directory traversal sequences such as ../ or ..\ that would normally be blocked by the open_basedir restrictions. The vulnerability essentially enables attackers to manipulate the glob function's behavior to access files outside the designated safe directories, effectively nullifying the security controls that were intended to prevent such unauthorized access. This type of vulnerability falls under CWE-22, which specifically addresses Improper Limiting of a Pathname to a Restricted Directory, commonly known as Path Traversal or Directory Traversal. The flaw demonstrates how seemingly innocuous file system functions can become security risks when not properly validated against boundary conditions and security constraints.
The operational impact of CVE-2007-4663 extends beyond simple unauthorized file access, as it can enable more sophisticated attacks including information disclosure, remote code execution, and system compromise. Attackers can leverage this vulnerability to access configuration files that may contain database credentials, API keys, or other sensitive information that could lead to further exploitation. The vulnerability is particularly dangerous in shared hosting environments or applications that rely heavily on open_basedir restrictions for security isolation. When combined with other vulnerabilities or exploitation techniques, this directory traversal flaw can serve as a gateway for attackers to escalate privileges and gain deeper access to the underlying system. The attack surface is significant because many PHP applications use the glob function for various operations, making this vulnerability widespread across numerous web applications and hosting environments. This aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter, where attackers can use such vulnerabilities to execute commands or access files that would normally be restricted.
Mitigation strategies for CVE-2007-4663 primarily focus on immediate software updates and proper configuration management. The most effective remediation is upgrading to PHP version 5.2.4 or later, where the vulnerability has been patched and the glob function properly validates input parameters. System administrators should also implement additional security controls including proper input validation, regular security audits, and monitoring for suspicious file access patterns. The open_basedir restrictions should be configured with the most restrictive settings possible, ensuring that only necessary directories are accessible to PHP applications. Additionally, implementing web application firewalls and intrusion detection systems can help detect and prevent exploitation attempts. Organizations should also conduct regular vulnerability assessments to identify and remediate similar issues in their PHP applications and ensure that all components are updated to supported versions. The vulnerability highlights the importance of proper input sanitization and the need for security testing of core functions like glob that handle file system operations. Security practices should include regular patch management procedures and adherence to secure coding guidelines that prevent similar path traversal vulnerabilities from being introduced into applications.