CVE-2004-0837 in MySQL
Summary
by MITRE
MySQL 4.x before 4.0.21, and 3.x before 3.23.49, allows attackers to cause a denial of service (crash or hang) via multiple threads that simultaneously alter MERGE table UNIONs.
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Analysis
by VulDB Data Team • 07/07/2025
The vulnerability described in CVE-2004-0837 represents a critical concurrency issue affecting MySQL database systems across multiple versions including 3.x series before 3.23.49 and 4.x series before 4.0.21. This flaw specifically targets MERGE table functionality which serves as a database abstraction layer allowing multiple tables to be treated as a single logical table. The vulnerability stems from improper handling of simultaneous thread operations when modifying MERGE table UNION structures, creating a condition where concurrent access patterns can trigger system instability.
The technical implementation of this vulnerability exploits race conditions within MySQL's table management subsystem, particularly when multiple threads attempt to modify MERGE table UNION clauses simultaneously. When these concurrent operations occur, the database engine fails to properly synchronize access to shared MERGE table structures, leading to memory corruption or deadlock conditions. This concurrency flaw operates at the kernel level of the database engine where table metadata and access structures are manipulated, making it particularly dangerous as it can cause complete system crashes or indefinite hangs that require manual intervention to resolve.
The operational impact of this vulnerability extends beyond simple service disruption to encompass potential data integrity risks and business continuity concerns. Organizations relying on MySQL for mission-critical applications face significant operational risks when this vulnerability exists in their systems, as the denial of service conditions can last for extended periods requiring system restarts and potential data recovery procedures. The vulnerability affects database performance and availability, making it particularly concerning for applications requiring high availability and consistent access to data. Attackers can exploit this weakness systematically by creating multiple concurrent threads that manipulate MERGE table structures, amplifying the impact of the denial of service condition.
Mitigation strategies for CVE-2004-0837 involve immediate patching of affected MySQL versions to the recommended secure releases, specifically upgrading to MySQL 3.23.49 or 4.0.21 and later versions. Organizations should also implement database access controls to limit concurrent operations on MERGE tables and consider implementing application-level throttling mechanisms to prevent excessive simultaneous access patterns. The vulnerability aligns with CWE-362, which describes concurrent execution use of lock, and may be related to ATT&CK techniques involving service stoppage and denial of service operations. Database administrators should conduct thorough testing of patched systems and implement monitoring solutions to detect unusual concurrent access patterns that might indicate exploitation attempts. Additionally, organizations should review their database architecture to minimize reliance on MERGE tables in high-concurrency environments where this vulnerability could pose significant operational risks.