CVE-2018-8740 in SQLite
Summary
by MITRE
In SQLite through 3.22.0, databases whose schema is corrupted using a CREATE TABLE AS statement could cause a NULL pointer dereference, related to build.c and prepare.c.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 02/22/2023
The vulnerability identified as CVE-2018-8740 represents a critical NULL pointer dereference flaw within SQLite database management system versions prior to 3.22.1. This issue manifests when processing databases with corrupted schemas that have been manipulated through CREATE TABLE AS statements, creating a scenario where the database engine fails to properly validate schema integrity before attempting to execute subsequent operations. The vulnerability specifically affects the build.c and prepare.c source code modules, which are responsible for database schema construction and statement preparation respectively, indicating a fundamental weakness in the database engine's schema validation mechanisms.
The technical exploitation of this vulnerability occurs when SQLite encounters a malformed database schema that has been artificially corrupted through the CREATE TABLE AS construct. During the preparation phase of database operations, the system attempts to access memory locations that have not been properly initialized or allocated, resulting in a NULL pointer dereference. This type of error typically occurs when the database engine assumes certain memory structures or schema elements exist when they have been corrupted or improperly constructed. The flaw falls under CWE-476 which specifically addresses NULL pointer dereference vulnerabilities, where an application attempts to access a memory location through a pointer that has not been properly initialized to point to valid memory.
The operational impact of CVE-2018-8740 extends beyond simple application crashes, as it represents a potential denial of service vector that could be exploited in environments where SQLite is used as a backend database. When triggered, the NULL pointer dereference causes the database engine to terminate unexpectedly, potentially leading to service disruption for applications relying on SQLite functionality. In multi-tenant or high-availability systems, this vulnerability could be leveraged to create persistent service interruptions. The vulnerability is particularly concerning in environments where database schema integrity cannot be guaranteed, as it demonstrates that malformed schema constructs can propagate through the database engine's preparation and building phases without adequate safeguards. The flaw also aligns with ATT&CK technique T1499.004 which involves network disruption through service availability attacks, as the vulnerability can be exploited to cause database service unavailability.
Mitigation strategies for CVE-2018-8740 primarily involve upgrading to SQLite version 3.22.1 or later, where the vulnerability has been addressed through improved schema validation and memory management. Organizations should implement comprehensive database schema validation procedures before deploying any CREATE TABLE AS operations, particularly in environments where external or untrusted data sources are involved. Additionally, implementing proper input sanitization and schema integrity checks can provide defense-in-depth measures against similar vulnerabilities. System administrators should also consider implementing monitoring and alerting mechanisms to detect unexpected database engine termination or memory access violations, as these may indicate exploitation attempts. The vulnerability highlights the importance of proper memory management and input validation in database engine implementations, particularly when handling schema construction and modification operations that could potentially create malformed database structures.