CVE-2019-19645 in SQLite
Summary
by MITRE
alter.c in SQLite through 3.30.1 allows attackers to trigger infinite recursion via certain types of self-referential views in conjunction with ALTER TABLE statements.
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Analysis
by VulDB Data Team • 03/09/2024
The vulnerability identified as CVE-2019-19645 represents a critical flaw in SQLite database management systems affecting versions through 3.30.1. This issue stems from improper handling of recursive structures within the database engine's processing of ALTER TABLE commands. The flaw specifically manifests when the database encounters self-referential views that create circular dependencies, leading to a condition where the system enters an infinite recursive loop during query execution. Such recursive processing occurs within the alter.c component of SQLite's source code, which governs table modification operations and view management functionalities.
The technical exploitation of this vulnerability occurs through carefully crafted database schema modifications that introduce self-referential views. When an ALTER TABLE statement is executed against a database containing such problematic views, the SQLite engine attempts to resolve the recursive references by repeatedly processing the same logical structures. This creates an unbounded recursion pattern that consumes system resources and eventually leads to denial of service conditions. The flaw is particularly insidious because it can be triggered through legitimate database operations without requiring elevated privileges or special user permissions. The recursive nature of the vulnerability means that even simple ALTER TABLE commands can cause the database engine to consume excessive CPU cycles and memory resources, effectively rendering the database service unavailable to legitimate users.
From an operational perspective, this vulnerability presents significant risks to applications that rely on SQLite for data storage and management. The infinite recursion condition can cause database processes to become unresponsive, leading to application downtime and potential data access failures. Systems running vulnerable SQLite versions may experience complete service disruption when malicious or malformed ALTER TABLE statements are processed, particularly in environments where automated database maintenance scripts or user-generated queries might inadvertently trigger the recursive condition. The impact extends beyond simple denial of service as the resource exhaustion can potentially affect system stability and performance of other applications sharing the same computing resources.
Security professionals should consider this vulnerability in the context of software supply chain risks, as SQLite is widely deployed across numerous applications and operating systems. The flaw aligns with CWE-674 principle of uncontrolled recursion, which describes situations where recursive operations lack proper termination conditions or depth limits. This vulnerability also relates to ATT&CK technique T1499.004, which covers network disruption through resource exhaustion attacks. Organizations should prioritize immediate patching of SQLite installations to version 3.30.2 or later, where the recursive loop detection and termination mechanisms have been implemented. Additional mitigations include implementing database query monitoring to detect unusual recursive patterns, restricting ALTER TABLE operations to trusted administrative users only, and employing database connection pooling with resource limits to prevent complete service exhaustion. The vulnerability serves as a reminder of the importance of proper recursion handling in database engine design and the potential for seemingly benign operations to trigger catastrophic system failures when not properly bounded.