CVE-2005-4736 in DB2 Universal Database
Summary
by MITRE
IBM DB2 Universal Database (UDB) 820 before 8.2 FP10 allows remote authenticated users to cause a denial of service (disk consumption) via a hash join (hsjn) that triggers an infinite loop in sqlri_hsjnFlushBlocks.
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Analysis
by VulDB Data Team • 07/07/2021
IBM DB2 Universal Database version 8.20 before fix pack 10 contains a critical vulnerability that enables authenticated remote attackers to consume excessive disk resources and cause denial of service conditions through a specific hash join operation. This vulnerability resides in the sqlri_hsjnFlushBlocks function which handles hash join processing, where an infinite loop occurs during the flush block operations. The flaw specifically affects the hash join algorithm implementation within the database engine's resource management subsystem, creating a condition where disk space consumption becomes unbounded as the system continuously processes hash join operations without proper termination conditions.
The technical implementation of this vulnerability stems from insufficient boundary checking and loop termination logic within the hash join processing module. When an authenticated user executes a carefully crafted query that triggers a hash join operation, the sqlri_hsjnFlushBlocks function enters an infinite loop that continuously allocates and processes blocks of data without proper exit conditions. This condition causes the database engine to consume disk space at an exponential rate as it attempts to flush hash join blocks to disk storage, ultimately exhausting available disk resources and rendering the database service unavailable to legitimate users. The vulnerability is particularly dangerous because it requires only authenticated access, making it exploitable by users with valid database credentials who may not have administrative privileges.
The operational impact of this vulnerability extends beyond simple denial of service to potentially compromise the entire database infrastructure. When the infinite loop occurs, it creates a cascading effect that consumes not only disk space but also system memory and processing resources, leading to complete system unresponsiveness. The resource exhaustion can affect other database operations and potentially cause system crashes or restarts, especially in environments where disk space is already constrained. This vulnerability directly impacts database availability and can result in significant business disruption, particularly in mission-critical applications where database uptime is essential for operations. The attack vector requires remote access and valid authentication credentials, but the impact can be severe enough to warrant immediate remediation.
Organizations should prioritize applying IBM fix pack 8.2 FP10 or later to address this vulnerability, as it contains the necessary code modifications to properly terminate hash join operations and prevent the infinite loop condition. System administrators should also implement monitoring solutions to detect unusual disk space consumption patterns that may indicate exploitation attempts. Database access controls should be reviewed to minimize the number of authenticated users with sufficient privileges to execute complex queries that could trigger hash join operations. The vulnerability aligns with CWE-835, which describes infinite loops in software systems, and can be categorized under ATT&CK technique T1499.004 for network denial of service attacks. Additionally, this vulnerability demonstrates the importance of proper resource management and loop termination validation in database engine implementations, highlighting the need for comprehensive code review processes and security testing of core database operations.