CVE-2016-6663 in XtraDB Cluster
Summary
by MITRE
Race condition in Oracle MySQL before 5.5.52, 5.6.x before 5.6.33, 5.7.x before 5.7.15, and 8.x before 8.0.1; MariaDB before 5.5.52, 10.0.x before 10.0.28, and 10.1.x before 10.1.18; Percona Server before 5.5.51-38.2, 5.6.x before 5.6.32-78-1, and 5.7.x before 5.7.14-8; and Percona XtraDB Cluster before 5.5.41-37.0, 5.6.x before 5.6.32-25.17, and 5.7.x before 5.7.14-26.17 allows local users with certain permissions to gain privileges by leveraging use of my_copystat by REPAIR TABLE to repair a MyISAM table.
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Analysis
by VulDB Data Team • 11/25/2024
This vulnerability represents a critical race condition affecting multiple database systems including Oracle MySQL, MariaDB, and Percona variants. The flaw exists in the handling of file permissions during table repair operations, specifically when the my_copystat function is invoked by REPAIR TABLE commands. The vulnerability allows local users with specific permissions to escalate their privileges through a timing-dependent flaw that occurs during the repair process of MyISAM tables. The race condition manifests when the database engine copies file statistics during repair operations, creating a window where malicious actors can manipulate the system state to gain elevated privileges.
The technical implementation of this vulnerability stems from improper synchronization mechanisms during the file system operations performed by the database engine. When REPAIR TABLE is executed on MyISAM tables, the system calls my_copystat which copies file metadata including ownership and permissions. The race condition occurs because the system does not properly validate or lock file permissions during this critical operation window. Attackers can exploit this by creating race conditions where they manipulate the file system state between the time when permissions are read and when they are applied, allowing them to bypass normal access controls. This type of vulnerability aligns with CWE-367 which specifically addresses Time-of-Check to Time-of-Use (TOCTOU) flaws, where the state of a resource changes between verification and actual use.
The operational impact of CVE-2016-6663 is significant for database administrators and system operators. Local users with minimal privileges can potentially escalate to administrative access, compromising the entire database system and potentially leading to data theft, modification, or complete system compromise. The vulnerability affects multiple database versions across different vendors, making it particularly dangerous in environments where various database products are deployed. Organizations running affected versions face the risk of unauthorized privilege escalation that could lead to complete system takeover, especially when database servers are running with elevated privileges or when multiple database instances exist within the same environment.
Mitigation strategies for this vulnerability require immediate patching of all affected database versions to the latest stable releases. Database administrators should also implement strict access controls and privilege management, ensuring that local users have minimal required permissions. System hardening measures including disabling unnecessary database features and implementing proper file system permissions can help reduce the attack surface. Monitoring for suspicious REPAIR TABLE operations and implementing intrusion detection systems can help identify potential exploitation attempts. Additionally, organizations should conduct thorough security audits of their database environments to identify and remediate similar race condition vulnerabilities in other database operations. The fix implemented by vendors typically involves proper locking mechanisms during file copy operations and enhanced validation of file permissions before privilege escalation occurs, addressing the underlying TOCTOU vulnerability pattern that makes this attack possible.