CVE-2023-22059: Oracle MySQL Server Optimizer DoS Flaw

CVE-2023-22059 Overview

CVE-2023-22059 is a Denial of Service vulnerability affecting the MySQL Server product of Oracle MySQL, specifically within the Server: Optimizer component. This vulnerability allows a low-privileged attacker with network access to exploit the MySQL Server through multiple protocols, resulting in a complete denial of service condition. Successful exploitation enables attackers to cause a hang or frequently repeatable crash of the MySQL Server, significantly impacting database availability.

Critical Impact

Attackers with low privileges can remotely crash MySQL Server instances, causing complete service disruption and potentially affecting all dependent applications and services.

Affected Products

• Oracle MySQL Server versions 8.0.34 and prior
• Oracle MySQL Server version 8.1.0
• NetApp OnCommand Insight (which incorporates affected MySQL versions)

Discovery Timeline

• 2023-10-17 - CVE-2023-22059 published to NVD
• 2023-10-17 - Oracle releases security patch in October 2023 Critical Patch Update
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-22059

Vulnerability Analysis

This vulnerability resides in the Server: Optimizer component of Oracle MySQL Server. The Optimizer is responsible for determining the most efficient execution plan for SQL queries. A flaw in this component allows authenticated users with minimal privileges to craft specific queries or operations that trigger resource exhaustion or undefined behavior within the optimizer logic.

The vulnerability is characterized by its ease of exploitation—no special conditions or user interaction are required beyond network access and basic authentication. The attack does not compromise data confidentiality or integrity; however, it severely impacts availability by enabling complete denial of service through server crashes or hangs.

Root Cause

The root cause stems from improper handling of certain query optimization scenarios within the MySQL Server Optimizer component. When processing specific query patterns or execution plans, the optimizer fails to properly validate or handle edge cases, leading to a crash or hang condition. The CWE classification indicates insufficient information is publicly available regarding the specific technical flaw (NVD-CWE-noinfo).

Attack Vector

The attack can be executed remotely over the network using multiple protocols supported by MySQL Server. An attacker needs only low-level privileges (such as a basic database user account) to exploit this vulnerability. The attack flow typically involves:

1. Establishing a network connection to the vulnerable MySQL Server instance
2. Authenticating with low-privileged credentials
3. Executing specially crafted queries that trigger the optimizer flaw
4. Causing the MySQL Server to hang or crash repeatedly

The vulnerability does not require user interaction and has an unchanged scope, meaning the impact is limited to the vulnerable MySQL Server component itself. However, the availability impact is considered high, as successful exploitation results in complete service denial.

Detection Methods for CVE-2023-22059

Indicators of Compromise

• Unexpected MySQL Server crashes or service restarts in system logs
• Repeated optimizer-related errors in MySQL error logs
• Unusual query patterns from low-privileged user accounts
• Abnormal resource utilization preceding server hangs

Detection Strategies

• Monitor MySQL error logs for recurring crash patterns related to the optimizer component
• Implement query auditing to detect anomalous SQL patterns from low-privileged accounts
• Deploy database activity monitoring solutions to track unusual connection and query behaviors
• Configure alerting for MySQL Server availability and uptime metrics

Monitoring Recommendations

• Enable MySQL slow query and error logging with appropriate retention
• Set up automated alerts for MySQL service interruptions or restarts
• Monitor database connection patterns for authentication attempts followed by crashes
• Implement network-level monitoring for unusual traffic patterns to MySQL ports (default 3306)

How to Mitigate CVE-2023-22059

Immediate Actions Required

• Apply the Oracle Critical Patch Update from October 2023 immediately
• Review and restrict network access to MySQL Server instances
• Audit user privileges and remove unnecessary low-privileged accounts
• Implement network segmentation to limit exposure of database servers

Patch Information

Oracle has addressed this vulnerability in the October 2023 Critical Patch Update. Affected organizations should upgrade to MySQL Server versions released after the October 2023 CPU. Detailed patch information is available in the Oracle Security Alert October 2023.

NetApp users should consult the NetApp Security Advisory NTAP-20231027-0009 for guidance on affected OnCommand Insight deployments.

Workarounds

• Restrict network access to MySQL Server using firewall rules to allow only trusted IP addresses
• Implement strict authentication policies and minimize the number of user accounts with database access
• Use connection pooling with limited privileges to reduce direct database exposure
• Consider deploying MySQL Server behind a reverse proxy or load balancer with rate limiting capabilities
• Enable MySQL Server audit logging to detect and respond to suspicious query patterns

# Configuration example - Restrict MySQL network binding and implement connection limits
# Edit MySQL configuration file (my.cnf or my.ini)

[mysqld]
# Bind MySQL to specific internal interface only
bind-address = 10.0.0.1

# Limit maximum connections to reduce DoS impact
max_connections = 100

# Set connection timeout to terminate hanging connections
wait_timeout = 300
interactive_timeout = 300

# Enable error logging for crash detection
log_error = /var/log/mysql/error.log

# Enable general query log for auditing (use with caution in production)
general_log = 1
general_log_file = /var/log/mysql/query.log