CVE-2011-5219 in mPDF
Summary
by MITRE
Directory traversal vulnerability in examples/show_code.php in mPDF 5.3 and earlier allows remote attackers to read arbitrary files via a .. (dot dot) in the filename parameter.
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Analysis
by VulDB Data Team • 12/26/2024
The CVE-2011-5219 vulnerability represents a critical directory traversal flaw discovered in mPDF version 5.3 and earlier, affecting the examples/show_code.php component of this popular PHP library used for generating PDF documents. This vulnerability stems from inadequate input validation within the filename parameter processing logic, creating a pathway for malicious actors to access arbitrary files on the server filesystem through crafted directory traversal sequences. The flaw specifically manifests when the application fails to properly sanitize user-supplied input before using it in file operations, allowing attackers to manipulate file paths and bypass normal access controls. The vulnerability's impact extends beyond simple information disclosure, as it can potentially enable attackers to read sensitive configuration files, source code, or other system resources that should remain protected. The directory traversal attack vector exploits the .. (dot dot) sequence in file paths to navigate upward through the directory structure, effectively breaking out of intended file access boundaries. This type of vulnerability is classified under CWE-22 as "Improper Limitation of a Pathname to a Restricted Directory" and aligns with ATT&CK technique T1083 for discovering system information through directory traversal methods. The mPDF library's use in web applications makes this vulnerability particularly dangerous as it can be exploited through web interfaces, potentially allowing attackers to gain unauthorized access to server resources and sensitive data. The vulnerability's exploitation requires minimal technical expertise, making it an attractive target for both skilled and less experienced attackers seeking to compromise web applications. Security researchers have identified that the flaw exists due to insufficient validation of the filename parameter in the show_code.php example script, which directly incorporates user input into file operations without proper sanitization or path restriction mechanisms.
The technical exploitation of CVE-2011-5219 occurs when an attacker submits a specially crafted filename parameter containing directory traversal sequences such as ../../etc/passwd or ../../../windows/system32/drivers/etc/hosts. The vulnerable code fails to validate or sanitize this input before using it in file operations, allowing the traversal sequences to be interpreted by the underlying operating system. This creates an opportunity for attackers to access files outside of the intended directory scope, potentially leading to information disclosure of system files, configuration data, or application source code. The vulnerability's impact is particularly severe in environments where the web application runs with elevated privileges or where sensitive files are stored in accessible locations. The flaw demonstrates a classic lack of proper input validation and access control measures that should be implemented in all file handling operations within web applications. Attackers can leverage this vulnerability to extract database connection details, application credentials, or other sensitive information that could lead to further compromise of the system. The vulnerability's persistence across multiple versions of mPDF indicates a fundamental flaw in the library's design approach to file handling and input validation, highlighting the importance of implementing robust security controls in open source components. Organizations using mPDF versions prior to the patched release face significant risk exposure, as the vulnerability can be exploited through simple HTTP requests without requiring authentication or specialized tools. The vulnerability's exploitation can be automated through various tools and techniques, making it particularly dangerous in environments where applications are not properly monitored for suspicious file access patterns.
Organizations affected by CVE-2011-5219 should implement immediate mitigations including upgrading to mPDF version 5.4 or later, which contains the necessary patches to address the directory traversal vulnerability. Additionally, administrators should review and restrict file access permissions on web servers, ensuring that applications cannot access sensitive system files or directories. Input validation should be implemented at multiple levels including application code, web server configuration, and network-level controls to prevent malicious traversal sequences from reaching vulnerable components. Security monitoring should be enhanced to detect unusual file access patterns or attempts to access system files through web interfaces. The vulnerability highlights the importance of proper secure coding practices including parameter validation, input sanitization, and access control enforcement. Organizations should also consider implementing web application firewalls and intrusion detection systems to help identify and block exploitation attempts. Regular security assessments and code reviews should be conducted to identify similar vulnerabilities in other components of the application stack. The incident underscores the critical need for maintaining up-to-date software libraries and implementing comprehensive security controls throughout the application lifecycle. Security teams should also establish incident response procedures specifically addressing file traversal vulnerabilities to ensure rapid response and remediation when similar issues are discovered. Organizations should conduct regular vulnerability assessments to identify unpatched systems and ensure that all components are running supported versions with appropriate security fixes. The vulnerability serves as a reminder of the importance of secure file handling practices and the potential consequences of inadequate input validation in web applications.