CVE-2011-0754 in PHP
Summary
by MITRE
The SplFileInfo::getType function in the Standard PHP Library (SPL) extension in PHP before 5.3.4 on Windows does not properly detect symbolic links, which might make it easier for local users to conduct symlink attacks by leveraging cross-platform differences in the stat structure, related to lack of a FILE_ATTRIBUTE_REPARSE_POINT check.
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Analysis
by VulDB Data Team • 10/13/2021
The vulnerability identified as CVE-2011-0754 represents a critical security flaw in PHP's Standard PHP Library (SPL) extension affecting versions prior to 5.3.4 on Windows operating systems. This issue stems from the SplFileInfo::getType function's inability to properly identify symbolic links, creating a significant attack vector for local adversaries seeking to exploit cross-platform inconsistencies in file system behavior. The flaw specifically manifests due to the absence of proper FILE_ATTRIBUTE_REPARSE_POINT checking within the Windows stat structure implementation, which fundamentally alters how symbolic links are recognized compared to Unix-like systems where such detection works correctly.
The technical implementation of this vulnerability exploits the fundamental differences between Windows and Unix-like file systems in their handling of symbolic links and reparse points. On Windows, symbolic links are implemented as reparse points that require specific attribute checking to identify properly, whereas PHP's pre-5.3.4 SPL implementation failed to perform this crucial FILE_ATTRIBUTE_REPARSE_POINT verification. This discrepancy creates a scenario where malicious users can manipulate file system operations by creating symbolic links that appear as regular files or directories to the vulnerable PHP functions, thereby bypassing intended security checks and access controls. The vulnerability operates at the core of file system abstraction layers where PHP's SPL extension interfaces with the underlying operating system's file system APIs, making it particularly dangerous for applications that rely on file type detection for security decisions.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass broader security implications for applications running on Windows PHP environments. Attackers can leverage this flaw to conduct symlink attacks that allow them to access files they would normally not have permission to read or execute, effectively bypassing file system access controls and potentially gaining unauthorized access to sensitive data or system resources. This vulnerability directly aligns with attack patterns described in the MITRE ATT&CK framework under the T1059.007 technique for "Command and Scripting Interpreter: PowerShell" and T1548.001 for "Abuse Elevation Control Mechanism: Bypass User Account Control," as it enables attackers to manipulate file system behavior to achieve unauthorized access. The flaw also relates to CWE-59, which describes improper handling of symbolic links, making it particularly dangerous in environments where PHP applications process user-supplied file paths or perform security-sensitive file operations.
Mitigation strategies for CVE-2011-0754 primarily focus on immediate version upgrading to PHP 5.3.4 or later, which includes the necessary fixes for proper symbolic link detection on Windows platforms. Organizations should also implement comprehensive patch management processes to ensure all PHP installations are updated promptly, particularly in environments where Windows servers host PHP applications. Additional defensive measures include implementing proper input validation and sanitization for file paths, utilizing alternative file system access methods that do not rely on the vulnerable SplFileInfo::getType function, and conducting thorough security audits of PHP applications to identify and remediate any code that depends on potentially vulnerable file type detection mechanisms. System administrators should also consider implementing monitoring solutions that can detect anomalous file system access patterns that might indicate exploitation attempts, as this vulnerability can be leveraged to bypass traditional security controls in PHP applications that depend on proper file type identification for access control decisions.