CVE-2008-4097 in MySQL
Summary
by MITRE
MySQL 5.0.51a allows local users to bypass certain privilege checks by calling CREATE TABLE on a MyISAM table with modified (1) DATA DIRECTORY or (2) INDEX DIRECTORY arguments that are associated with symlinks within pathnames for subdirectories of the MySQL home data directory, which are followed when tables are created in the future. NOTE: this vulnerability exists because of an incomplete fix for CVE-2008-2079.
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Analysis
by VulDB Data Team • 08/02/2021
This vulnerability in MySQL 5.0.51a represents a significant privilege escalation flaw that allows local attackers to bypass critical access controls through careful manipulation of table creation operations. The issue stems from insufficient validation of directory paths when creating MyISAM tables, specifically when the DATA DIRECTORY or INDEX DIRECTORY parameters contain symlinks that point to locations outside the designated MySQL data directory. This weakness enables unauthorized users to create tables in directories where they would normally not have write permissions, effectively circumventing the database's security model. The vulnerability is particularly concerning because it operates at the file system level, leveraging the operating system's symlink resolution mechanisms to achieve unauthorized access. The flaw manifests when MySQL processes table creation requests that include directory specifications containing symbolic links, allowing the database engine to follow these links and place table files in unintended locations. This creates a pathway for local users to bypass privilege checks that should normally restrict table creation to specific directories, potentially enabling them to write to restricted areas of the file system or create malicious table structures.
The technical implementation of this vulnerability involves the interaction between MySQL's table creation logic and the underlying operating system's file handling mechanisms. When a user executes a CREATE TABLE statement with DATA DIRECTORY or INDEX DIRECTORY clauses that reference symlinks, the MySQL server follows these symbolic links during the table creation process. The system's path resolution occurs before privilege validation, meaning that even though the user might not have direct access to the final target location, the symlink traversal allows the operation to succeed. This behavior creates a race condition and path traversal vulnerability where the security checks occur on the symbolic link itself rather than on the ultimate target location. The vulnerability specifically affects MyISAM tables because of how they handle file placement and directory management, unlike other storage engines that might implement stricter path validation. The incomplete fix for CVE-2008-2079, which was supposed to address similar symlink-related privilege escalation issues, failed to cover all possible attack vectors, leaving this particular variant unaddressed. This oversight demonstrates how complex security fixes can have gaps that attackers can exploit by finding alternative paths to achieve the same objective.
The operational impact of this vulnerability extends beyond simple privilege escalation to potentially enable more serious security compromises within database environments. Local attackers who can execute CREATE TABLE statements can use this flaw to place malicious table files in locations where they might gain elevated privileges or access to sensitive data. The vulnerability could allow for data exfiltration, modification of database files, or even the creation of backdoor-like structures within the database system. Attackers might leverage this to establish persistent access or to manipulate database metadata in ways that could compromise the integrity of the entire database environment. The vulnerability is particularly dangerous in multi-user environments where different users have varying levels of access to the database system, as it could allow lower-privilege users to gain access to areas they should not be able to reach. Additionally, the vulnerability could be exploited in conjunction with other weaknesses to create more complex attack scenarios, potentially leading to complete system compromise. The fact that this vulnerability exists in the MySQL 5.0.51a version indicates a long-standing issue that could have affected numerous production environments, making it a critical concern for system administrators managing legacy database installations.
Organizations should implement immediate mitigations to address this vulnerability, including upgrading to patched versions of MySQL that properly resolve the symlink handling issues. System administrators must also conduct thorough audits of their MySQL installations to identify any instances where symlinks might be present in data or index directory paths. The recommended approach involves disabling the use of symlinks in table directory specifications and ensuring that all directory paths are properly validated before table creation operations are permitted. Security configurations should be reviewed to ensure that the MySQL data directory and all subdirectories are properly secured with appropriate file permissions. Additionally, monitoring should be implemented to detect any attempts to create tables with suspicious directory specifications, particularly those that might contain symbolic links. Organizations should also consider implementing additional security controls such as mandatory access controls or file integrity monitoring systems to detect unauthorized modifications to database files. The vulnerability demonstrates the importance of comprehensive security testing, particularly for complex database systems where file system interactions can create unexpected security implications. Regular security assessments and vulnerability scanning should be conducted to identify similar issues that might exist in other database components or related systems. This vulnerability also highlights the necessity of maintaining current security patches and the importance of understanding the complete scope of security fixes, as partial solutions can leave systems vulnerable to exploitation through alternative attack vectors.