CVE-2010-3436 in PHP
Summary
by MITRE
fopen_wrappers.c in PHP 5.3.x through 5.3.3 might allow remote attackers to bypass open_basedir restrictions via vectors related to the length of a filename.
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Analysis
by VulDB Data Team • 09/28/2021
The vulnerability identified as CVE-2010-3436 represents a critical security flaw in PHP's file handling mechanisms that could potentially allow remote attackers to circumvent important security restrictions. This issue specifically affects PHP versions 5.3.0 through 5.3.3 and resides within the fopen_wrappers.c source file, which governs how PHP handles file operations and access controls. The vulnerability stems from a flaw in how PHP processes filename lengths during file operations, creating an avenue for attackers to bypass the open_basedir directive that is designed to limit which files a script can access.
The technical exploitation of this vulnerability occurs through carefully crafted filename lengths that manipulate the internal file handling logic of PHP. When PHP processes file operations, it performs validation checks against the open_basedir restrictions to ensure that file access remains within designated boundaries. However, the flaw in the fopen_wrappers.c implementation allows attackers to construct filenames of specific lengths that can trick the validation mechanism into accepting file operations that should otherwise be blocked. This creates a condition where remote attackers can access files outside the intended directory boundaries, potentially leading to unauthorized data access, information disclosure, or even system compromise.
The operational impact of this vulnerability extends beyond simple file access violations and represents a significant threat to web application security. Attackers could leverage this flaw to access sensitive files that should be protected by open_basedir restrictions, including configuration files, database credentials, or other system files that contain confidential information. The vulnerability is particularly dangerous in shared hosting environments where multiple applications run on the same server, as it could allow one application to access files belonging to other applications or even system-level files. This bypass of security controls undermines the fundamental principle of least privilege and could lead to complete system compromise if combined with other vulnerabilities or if the targeted files contain sensitive authentication information.
This vulnerability aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal attacks. The flaw specifically relates to how PHP handles pathname validation during file operations, creating a scenario where the security boundary defined by open_basedir can be circumvented through manipulation of filename length parameters. From an attacker's perspective, this vulnerability maps to techniques described in the ATT&CK framework under T1059 for command and scripting interpreter and T1566 for credential access, as it provides pathways for unauthorized file access that could lead to credential disclosure or further system compromise. The vulnerability also intersects with T1213, which covers data from information repositories, as it enables attackers to extract data from restricted locations that should be protected from unauthorized access.
Mitigation strategies for this vulnerability require immediate patching of affected PHP installations to versions that contain the necessary security fixes. System administrators should ensure that all PHP installations are updated to versions 5.3.4 or later, where the vulnerability has been addressed through improved filename length validation and enhanced open_basedir enforcement mechanisms. Additionally, organizations should implement additional security layers including proper input validation, regular security audits, and monitoring for suspicious file access patterns. The configuration of open_basedir should be reviewed to ensure it is properly enforced and that all applications are running with minimal required permissions. Network-level firewalls and intrusion detection systems should be configured to monitor for unusual file access patterns that might indicate exploitation attempts. Regular security assessments and vulnerability scanning should be conducted to identify any remaining exposure points and ensure that the security controls remain effective against evolving threats.