CVE-2021-29763 in DB2
Summary
by MITRE • 09/16/2021
IBM Db2 for Linux, UNIX and Windows (includes Db2 Connect Server) 11.1 and 11.5 under very specific conditions, could allow a local user to keep running a procedure that could cause the system to run out of memory.and cause a denial of service. IBM X-Force ID: 202267.
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Analysis
by VulDB Data Team • 09/19/2021
The vulnerability identified as CVE-2021-29763 affects IBM Db2 for Linux, UNIX and Windows database systems including the Db2 Connect Server component. This issue manifests specifically under certain conditions where a local user can exploit a procedural execution flaw that leads to excessive memory consumption. The vulnerability resides within the database management system's handling of certain procedures, creating a scenario where memory allocation continues unchecked until system resources are exhausted. The flaw represents a denial of service condition that can severely impact database availability and system stability.
The technical implementation of this vulnerability involves the improper management of memory resources during procedure execution within the Db2 database engine. When specific conditions are met, the system fails to properly terminate or limit memory allocation for ongoing procedures, allowing malicious or compromised local users to potentially exploit this behavior. The flaw demonstrates characteristics consistent with memory leak vulnerabilities where allocated resources are not properly released back to the system. According to CWE classification, this vulnerability aligns with CWE-401: Improper Release of Memory Before Removing Last Reference, which describes situations where memory is not properly deallocated leading to resource exhaustion.
The operational impact of this vulnerability extends beyond simple resource consumption as it can result in complete system unavailability. When memory exhaustion occurs, the database server becomes unresponsive to legitimate requests, causing cascading failures throughout dependent applications and services. This type of denial of service attack can be particularly damaging in production environments where database availability is critical for business operations. The vulnerability's condition specificity means that exploitation requires particular system states or procedure calls, but once triggered, the impact can be severe and difficult to recover from without manual intervention or system restarts.
Mitigation strategies for this vulnerability should focus on immediate patching from IBM as the primary solution, as the flaw exists within the core database engine functionality. Organizations should implement monitoring solutions to detect unusual memory consumption patterns that could indicate exploitation attempts. Access controls and privilege management should be reviewed to limit local user access to database procedures that might trigger this behavior. The ATT&CK framework categorizes this vulnerability under T1499.004: Endpoint Denial of Service - Network Denial of Service, where the attack vector involves local system resources rather than network-based attacks. System administrators should also consider implementing resource limits and memory constraints on database procedures to prevent unbounded resource consumption even if the underlying vulnerability remains unpatched.