CVE-2020-35525: SQLite NULL Pointer Dereference Flaw

CVE-2020-35525 Overview

CVE-2020-35525 is a Null Pointer Dereference vulnerability affecting SQLite version 3.31.1. A potential null pointer dereference was identified in the INTERSECT query processing functionality, which can lead to denial of service conditions when exploited. This vulnerability allows remote attackers to crash applications that use vulnerable versions of SQLite by sending specially crafted SQL queries containing INTERSECT operations.

Critical Impact

Successful exploitation of this vulnerability can cause application crashes and denial of service, affecting system availability for any application relying on SQLite for database operations.

Affected Products

• SQLite 3.31.1
• Applications and systems embedding SQLite 3.31.1
• NetApp products using affected SQLite versions (see NetApp Security Advisory NTAP-20230706-0007)

Discovery Timeline

• 2022-09-01 - CVE-2020-35525 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2020-35525

Vulnerability Analysis

This vulnerability is classified as CWE-476 (NULL Pointer Dereference), a memory corruption flaw that occurs when a program attempts to dereference a pointer that has a null value. In the context of SQLite, this manifests during the processing of INTERSECT queries, where improper validation of internal data structures leads to potential null pointer access.

The vulnerability can be triggered remotely through network-accessible applications that process user-supplied SQL queries. No authentication is required to exploit this flaw, and the attack complexity is low, making it relatively straightforward for attackers to trigger. While this vulnerability does not allow data exfiltration or modification, it can cause complete denial of service to affected applications.

Root Cause

The root cause of CVE-2020-35525 lies in insufficient null pointer validation within SQLite's INTERSECT query processing code path. When processing certain INTERSECT queries, the SQLite engine fails to properly check whether internal data structure pointers are valid before dereferencing them. This oversight allows a null pointer to be accessed, triggering a segmentation fault and causing the application to crash.

The issue was identified and documented in the SQLite source repository.

Attack Vector

The attack vector for this vulnerability is network-based. An attacker can exploit this flaw by:

1. Identifying an application that accepts SQL queries from external sources and uses a vulnerable version of SQLite
2. Crafting a malicious SQL query containing an INTERSECT operation designed to trigger the null pointer condition
3. Submitting the query to the target application
4. The SQLite engine processes the query and encounters the null pointer dereference, causing the application to crash

The vulnerability requires no user interaction and can be exploited without any privileges, making it suitable for denial of service attacks against publicly accessible services using SQLite as their backend database.

Detection Methods for CVE-2020-35525

Indicators of Compromise

• Unexpected application crashes or restarts in services using SQLite
• Segmentation fault errors in application logs associated with database operations
• Anomalous SQL queries containing INTERSECT operations in query logs
• Core dump files indicating crashes within SQLite library code paths

Detection Strategies

• Implement SQL query logging and analysis to identify suspicious INTERSECT query patterns
• Monitor application stability metrics for unexpected crashes related to database operations
• Deploy runtime application self-protection (RASP) to detect exploitation attempts
• Use SentinelOne's behavioral AI to identify anomalous process terminations associated with SQLite-dependent applications

Monitoring Recommendations

• Enable verbose logging for SQLite query processing in affected applications
• Configure crash reporting and core dump analysis for SQLite-dependent services
• Implement application performance monitoring (APM) to track database operation failures
• Set up alerts for repeated application crashes that may indicate active exploitation

How to Mitigate CVE-2020-35525

Immediate Actions Required

• Upgrade SQLite to a version newer than 3.31.1 that includes the fix
• Review all applications in your environment that embed or depend on SQLite
• Implement input validation to sanitize SQL queries before processing
• Consider implementing rate limiting on SQL query endpoints to reduce DoS impact

Patch Information

SQLite has addressed this vulnerability in versions released after 3.31.1. The fix involves adding proper null pointer validation checks before dereferencing pointers during INTERSECT query processing. Technical details about the fix can be found in the SQLite source repository commit.

Organizations using NetApp products should also review the NetApp Security Advisory for guidance on affected products and available patches.

Workarounds

• Restrict access to SQL query interfaces from untrusted networks where feasible
• Implement application-level query validation to filter potentially malicious INTERSECT queries
• Deploy web application firewalls (WAF) with rules to detect unusual SQL query patterns
• Consider running SQLite-dependent applications in sandboxed environments to limit crash impact