CVE-2020-15358: SQLite Buffer Overflow Vulnerability

CVE-2020-15358 Overview

CVE-2020-15358 is a heap overflow vulnerability in SQLite versions prior to 3.32.3, caused by improper handling of query-flattener optimization in the select.c module. The vulnerability stems from the misuse of transitive properties during constant propagation, which leads to a multiSelectOrderBy heap overflow condition. This memory corruption vulnerability can be exploited locally to cause denial of service through application crashes.

Critical Impact
Local attackers can trigger a heap overflow in SQLite's query optimizer, potentially causing denial of service in applications that process untrusted SQL queries. Given SQLite's widespread use across operating systems, mobile platforms, and enterprise applications, this vulnerability has a broad attack surface.

Affected Products

SQLite (versions prior to 3.32.3)
Apple iOS, iPadOS, macOS, tvOS, watchOS, and iCloud for Windows
Canonical Ubuntu Linux 20.04 LTS
Oracle MySQL, Communications Messaging Server, and Enterprise Manager Ops Center
Oracle Communications Cloud Native Core Policy and Communications Network Charging and Control
Siemens SINEC Infrastructure Network Services

Discovery Timeline

June 27, 2020 - CVE-2020-15358 published to NVD
November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2020-15358

Vulnerability Analysis

This vulnerability exists within SQLite's query optimization subsystem, specifically in the select.c source file. The query-flattener is an optimization technique used to simplify nested SELECT statements by merging subqueries into the outer query when certain conditions are met. However, the implementation incorrectly applies transitive properties during constant propagation, leading to memory safety violations.

When processing complex queries with multiple SELECT statements and ORDER BY clauses, the optimizer's multiSelectOrderBy function can write beyond allocated heap buffer boundaries. This out-of-bounds write occurs because the constant propagation logic makes incorrect assumptions about data relationships, resulting in buffer size miscalculations.

The vulnerability requires local access and the ability to execute crafted SQL statements against a vulnerable SQLite instance. While the primary impact is denial of service through application crashes, heap overflow vulnerabilities can potentially be leveraged for more severe attacks depending on the exploitation context and memory layout.

Root Cause

The root cause lies in the query-flattener's constant propagation logic within select.c. When the optimizer attempts to flatten nested queries, it uses transitive properties to propagate constant values across query boundaries. The flaw occurs when these transitive relationships are incorrectly applied, causing the multiSelectOrderBy function to miscalculate buffer sizes needed for ordering operations. This results in heap memory being overwritten beyond its allocated bounds when processing ORDER BY clauses across multiple SELECT statements.

Attack Vector

The attack requires local access to execute SQL queries against a SQLite database. An attacker must craft a malicious SQL query that triggers the vulnerable code path in the query optimizer. The query would typically involve:

Multiple nested SELECT statements that qualify for query flattening
ORDER BY clauses that exercise the multiSelectOrderBy optimization
Constant values or expressions that trigger the faulty transitive property handling

Applications that process untrusted SQL input or allow users to construct complex queries are most at risk. This includes database management tools, content management systems with custom query interfaces, and applications embedding SQLite for local data storage.

The vulnerability mechanism can be understood by examining how the query optimizer processes nested SELECT statements with ORDER BY clauses. When flattening occurs, the constant propagation incorrectly calculates buffer requirements, leading to the heap overflow condition. For detailed technical information, see the SQLite Ticket View and the SQLite Version Change Timeline.

Detection Methods for CVE-2020-15358

Indicators of Compromise

Application crashes or unexpected terminations in processes using SQLite for database operations
Memory corruption errors or segmentation faults in applications with SQLite dependencies
Abnormal SQL query patterns involving deeply nested SELECT statements with ORDER BY clauses
Core dumps or crash logs indicating heap memory violations in SQLite library functions

Detection Strategies

Monitor for SQLite-related crashes using application crash reporting systems and process monitors
Implement input validation for SQL queries to detect complex nested SELECT statements with ORDER BY clauses
Use memory sanitizers (AddressSanitizer, Valgrind) during development and testing to identify heap overflows
Deploy application-level logging to capture and analyze SQL query patterns before execution

Monitoring Recommendations

Enable crash reporting and alerting for applications that depend on SQLite for data storage
Implement SQL query complexity limits to prevent excessively nested or complex queries
Monitor system logs for segmentation faults or memory access violations in SQLite-dependent processes
Track SQLite library versions across the environment to identify vulnerable deployments

How to Mitigate CVE-2020-15358

Immediate Actions Required

Upgrade SQLite to version 3.32.3 or later across all affected systems and applications
Apply vendor patches for affected Apple operating systems (iOS, iPadOS, macOS, tvOS, watchOS) and iCloud for Windows
Update Canonical Ubuntu Linux 20.04 LTS using the security update referenced in USN-4438-1
Apply Oracle Critical Patch Updates for affected Oracle products including MySQL and Communications components
Update Siemens SINEC Infrastructure Network Services per Siemens Security Advisory SSA-389290

Patch Information

The vulnerability was addressed in SQLite version 3.32.3. The fix corrects the transitive property handling in the constant propagation logic within the query-flattener optimization. Detailed commit information is available at the SQLite Version Information page.

Multiple vendors have released patches:

Apple: Security updates documented in HT211843, HT211844, HT211847, HT211850, HT211931, and HT212147
Oracle: Addressed in October 2020, January 2021, April 2021, and April 2022 Critical Patch Updates
Gentoo: See GLSA 202007-26
NetApp: Referenced in NTAP-20200709-0001

Workarounds

Restrict the ability to execute arbitrary SQL queries in affected applications where patching is not immediately possible
Implement query complexity limits to reject deeply nested SELECT statements
Deploy application-level sandboxing to limit the impact of potential crashes or memory corruption
Consider disabling query-flattener optimization if the SQLite build configuration allows (not recommended for production)

bash

# Check current SQLite version
sqlite3 --version

# On Ubuntu/Debian, update SQLite
sudo apt-get update
sudo apt-get install sqlite3 libsqlite3-0

# Verify the update
sqlite3 --version
# Should show 3.32.3 or later