CVE-2023-26021 in DB2
Summary
by MITRE • 04/28/2023
IBM Db2 for Linux, UNIX and Windows (includes Db2 Connect Server) 11.1 and 11.5 is vulnerable to a denial of service as the server may crash when compiling a specially crafted SQL query using a LIMIT clause. IBM X-Force ID: 247864.
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Analysis
by VulDB Data Team • 04/28/2023
The vulnerability identified as CVE-2023-26021 affects IBM Db2 for Linux, UNIX and Windows database systems including the Db2 Connect Server versions 11.1 and 11.5. This represents a critical denial of service weakness that can be exploited through careful crafting of SQL queries containing LIMIT clauses, potentially causing the database server to crash and become unavailable to legitimate users. The vulnerability resides within the query compilation process where specific combinations of LIMIT parameters trigger unexpected behavior in the database engine's parsing and execution logic.
The technical flaw manifests when the Db2 server attempts to process specially constructed SQL queries that utilize the LIMIT clause in conjunction with certain complex expressions or subqueries. This particular weakness stems from inadequate input validation and error handling within the query optimizer component of the database system. The vulnerability operates at the application layer and can be exploited remotely without requiring authentication, making it particularly dangerous in production environments where database availability is critical for business operations. The issue falls under CWE-129, which addresses improper validation of length of input buffers, and also aligns with ATT&CK technique T1499.004 for network denial of service attacks.
The operational impact of this vulnerability extends beyond simple service interruption as it can lead to significant business disruption when database servers crash and require manual intervention to restart. Organizations relying on Db2 for critical applications may experience extended downtime during incident response, potentially affecting data availability and application performance across multiple dependent systems. The vulnerability affects both the standard Db2 server installations and the Db2 Connect Server components, indicating a broad attack surface that spans different deployment scenarios. Recovery from such incidents typically requires database administrator intervention to restart services and may involve log analysis to identify the specific triggering query patterns.
Mitigation strategies should prioritize immediate patch application from IBM as the primary defense mechanism, since the vulnerability exists in the core database engine functionality. Organizations should implement network segmentation and access controls to limit exposure of database servers to untrusted networks while monitoring for unusual query patterns that might indicate exploitation attempts. Database administrators should consider implementing query monitoring and logging to detect potentially malicious SQL statements before they can trigger the vulnerability. Additional protective measures include disabling unnecessary database features, implementing proper input validation at the application layer, and maintaining regular backup and recovery procedures to minimize downtime impact. The vulnerability also highlights the importance of regular security assessments and penetration testing to identify similar weaknesses in database configurations and access controls that could be leveraged for more sophisticated attacks.