CVE-2007-0448 in PHP
Summary
by MITRE
The fopen function in PHP 5.2.0 does not properly handle invalid URI handlers, which allows context-dependent attackers to bypass safe_mode restrictions and read arbitrary files via a file path specified with an invalid URI, as demonstrated via the srpath URI.
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Analysis
by VulDB Data Team • 04/13/2025
The vulnerability described in CVE-2007-0448 represents a critical security flaw in PHP 5.2.0's handling of file operations within the fopen function. This issue stems from inadequate validation of URI handlers, creating a pathway for malicious actors to circumvent the safe_mode protection mechanisms that are designed to restrict file access in PHP environments. The vulnerability specifically manifests when PHP encounters file paths that contain invalid URI schemes, allowing attackers to manipulate the file access behavior through carefully crafted URI specifications. The demonstration using the srpath URI highlights how this flaw can be exploited in practice to gain unauthorized access to files that should normally be protected by safe_mode restrictions.
The technical implementation of this vulnerability involves PHP's failure to properly sanitize or validate URI schemes when processing file paths through the fopen function. When an attacker provides a file path containing an invalid URI handler such as srpath, PHP's internal parsing logic does not adequately distinguish between legitimate and malicious URI formats. This parsing inconsistency allows the system to interpret the URI in a manner that bypasses the normal file access controls. The vulnerability operates at the intersection of URI parsing and file system access control, where the insecure implementation creates a condition where invalid URI schemes can be leveraged to perform file operations that would otherwise be restricted. This represents a classic case of improper input validation that leads to privilege escalation through file access manipulation.
The operational impact of this vulnerability extends beyond simple file reading capabilities, as it fundamentally undermines the security model that safe_mode is intended to provide. Attackers can leverage this flaw to access sensitive files such as configuration files, database credentials, or other system resources that should remain protected from unauthorized access. The context-dependent nature of the attack means that exploitation requires specific conditions where the target system processes file paths through the vulnerable fopen function with invalid URI schemes. This vulnerability affects systems running PHP 5.2.0 where safe_mode is enabled, creating a scenario where the security mechanism designed to protect against unauthorized file access becomes ineffective. The implications are particularly severe in shared hosting environments or multi-tenant systems where proper file isolation is critical for maintaining security boundaries.
Security professionals should implement immediate mitigations including updating to PHP versions that address this vulnerability, typically PHP 5.2.1 or later, which contain proper URI validation logic. Additionally, administrators should review all file access operations within their PHP applications to ensure that input validation is properly implemented and that URI schemes are validated before processing. The vulnerability aligns with CWE-20, which describes improper input validation, and can be mapped to ATT&CK technique T1059.007 for execution through PHP scripts. Organizations should also consider implementing network-level protections such as web application firewalls that can detect and block suspicious URI patterns, while maintaining strict monitoring of file access operations that might indicate exploitation attempts. The remediation process should include thorough code reviews to identify other potential URI handling vulnerabilities and ensure that all file access operations properly validate their inputs before proceeding with any file system operations.