CVE-2018-20506 in macOS
Summary
by MITRE
SQLite before 3.25.3, when the FTS3 extension is enabled, encounters an integer overflow (and resultant buffer overflow) for FTS3 queries in a "merge" operation that occurs after crafted changes to FTS3 shadow tables, allowing remote attackers to execute arbitrary code by leveraging the ability to run arbitrary SQL statements (such as in certain WebSQL use cases). This is a different vulnerability than CVE-2018-20346.
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Analysis
by VulDB Data Team • 07/03/2023
The vulnerability identified as CVE-2018-20506 represents a critical integer overflow flaw within the SQLite database engine version 3.25.2 and earlier, specifically affecting systems utilizing the FTS3 full-text search extension. This vulnerability manifests during merge operations that occur when FTS3 shadow tables are modified with crafted inputs, creating a condition where integer arithmetic operations exceed their maximum representable values. The flaw exists in the database engine's handling of FTS3 query processing, where the merge operation between different index segments fails to properly validate integer values, leading to a cascading buffer overflow condition. The vulnerability is particularly concerning because it can be exploited remotely through SQL injection attacks, allowing attackers with the ability to execute arbitrary SQL statements to gain code execution privileges on the affected system.
The technical implementation of this vulnerability stems from improper bounds checking within the FTS3 extension's merge algorithm. When FTS3 shadow tables are modified through crafted SQL statements, the system performs internal calculations to determine memory allocation for merge operations. These calculations involve integer arithmetic that does not properly validate against overflow conditions, particularly when dealing with large data sets or complex merge scenarios. The overflow occurs in the memory management subsystem where the system calculates buffer sizes based on integer values derived from FTS3 metadata. When these calculations overflow, they result in insufficient buffer allocation, causing subsequent memory writes to overwrite adjacent memory regions. This memory corruption directly enables arbitrary code execution through carefully crafted FTS3 queries that trigger the vulnerable merge operation path, making it a classic buffer overflow vulnerability that can be leveraged for remote code execution.
The operational impact of CVE-2018-20506 extends across numerous attack vectors where SQLite databases with FTS3 extensions are deployed, particularly in web applications using WebSQL APIs or embedded systems with SQLite integration. Web applications that allow user input to be processed through FTS3 queries create an ideal exploitation environment where attackers can manipulate FTS3 shadow tables through SQL injection techniques. The vulnerability affects systems where FTS3 is enabled and where users can execute arbitrary SQL statements, which commonly occurs in WebSQL contexts where database operations are exposed to untrusted input. Security implications include potential data breaches, privilege escalation, and complete system compromise when the vulnerability is successfully exploited. The attack surface is particularly broad given SQLite's widespread use in mobile applications, embedded systems, and web browsers, where FTS3 functionality is frequently enabled to support full-text search capabilities.
Mitigation strategies for CVE-2018-20506 primarily focus on upgrading to SQLite version 3.25.3 or later, where the integer overflow vulnerability has been addressed through proper bounds checking in the FTS3 merge operations. Organizations should implement comprehensive patch management procedures to ensure all affected systems receive the security update promptly. Additional defensive measures include disabling FTS3 functionality when not required, implementing strict input validation for SQL operations, and monitoring database logs for suspicious FTS3 query patterns that might indicate exploitation attempts. Network segmentation and access controls should be enforced to limit the potential impact of successful exploitation, particularly in environments where database administrators have elevated privileges. The vulnerability aligns with CWE-190, which categorizes integer overflow conditions, and can be mapped to ATT&CK technique T1059.007 for script-based exploitation and T1074.001 for data staging through database manipulation. Organizations should also consider implementing database activity monitoring solutions that can detect anomalous FTS3 query patterns and potential exploitation attempts, as these systems can provide early warning indicators of vulnerability exploitation.
This vulnerability demonstrates the importance of thorough input validation and memory management in database engine implementations, particularly when dealing with complex indexing and search operations. The flaw highlights the critical need for robust integer overflow protection in systems that process user-supplied data through database operations, as even seemingly benign database extensions can become attack vectors when proper security controls are absent. The vulnerability's classification as a remote code execution flaw underscores the necessity of maintaining up-to-date database software and implementing defense-in-depth strategies to protect against sophisticated attack vectors that leverage database engine weaknesses.