CVE-2023-21977 Overview
CVE-2023-21977 is a vulnerability in the MySQL Server product of Oracle MySQL, specifically affecting the Server: Optimizer component. This easily exploitable vulnerability allows a high privileged attacker with network access via multiple protocols to compromise MySQL Server, resulting in an unauthorized ability to cause a hang or frequently repeatable crash (complete denial of service) of the MySQL Server.
Critical Impact
Successful exploitation allows attackers with administrative privileges to cause complete denial of service, resulting in database unavailability and potential business disruption.
Affected Products
- Oracle MySQL Server version 8.0.32 and prior
- Oracle MySQL (all editions with Server: Optimizer component)
- Systems running affected MySQL versions with network exposure
Discovery Timeline
- April 18, 2023 - CVE-2023-21977 published to NVD
- November 21, 2024 - Last updated in NVD database
Technical Details for CVE-2023-21977
Vulnerability Analysis
This vulnerability resides in the Server: Optimizer component of MySQL Server, which is responsible for query optimization and execution plan generation. The flaw allows a privileged attacker to trigger conditions that cause the database server to hang or crash repeatedly. While the vulnerability requires high privileges (such as database administrator access), it can be exploited remotely over the network through standard MySQL protocols.
The attack does not require user interaction and can be executed with low complexity once the attacker has established authenticated access with sufficient privileges. The impact is limited to availability—there is no unauthorized access to or modification of data.
Root Cause
The vulnerability stems from improper handling within the query optimizer component. When certain query patterns or optimization scenarios are processed, the optimizer fails to properly manage resources or handle edge cases, leading to a denial of service condition. The specific technical details have not been fully disclosed by Oracle, as indicated by the CWE classification of NVD-CWE-noinfo.
Attack Vector
The attack vector is network-based, meaning an attacker can exploit this vulnerability remotely without physical access to the target system. The attacker must have high privileges on the MySQL Server (such as administrative or DBA-level access) to execute the attack. Once these conditions are met, the attacker can send specially crafted queries or commands through multiple supported protocols to trigger the denial of service condition.
The exploitation does not require any interaction from legitimate users, making it a reliable attack vector for disrupting database availability once administrative access has been obtained.
Detection Methods for CVE-2023-21977
Indicators of Compromise
- Unexpected MySQL Server crashes or service restarts without apparent cause
- Repeated hang conditions in the MySQL Server requiring manual intervention
- Unusual query patterns from privileged accounts targeting optimizer functions
- Elevated error rates in MySQL error logs related to optimizer operations
Detection Strategies
- Monitor MySQL error logs for optimizer-related crash dumps or hang indicators
- Implement query auditing for privileged accounts to detect unusual query patterns
- Deploy database activity monitoring (DAM) solutions to track administrative actions
- Configure alerting for MySQL service availability and unexpected restarts
Monitoring Recommendations
- Enable MySQL audit logging to capture all privileged user activities
- Set up automated monitoring for MySQL process health and service availability
- Review MySQL error logs regularly for optimizer-related warnings or errors
- Implement real-time alerting for database downtime or repeated crash events
How to Mitigate CVE-2023-21977
Immediate Actions Required
- Upgrade MySQL Server to version 8.0.33 or later as recommended by Oracle
- Review and restrict network access to MySQL Server using firewall rules
- Audit privileged user accounts and apply principle of least privilege
- Implement monitoring for unusual administrative activity on database servers
Patch Information
Oracle has addressed this vulnerability in their April 2023 Critical Patch Update. Administrators should apply the security patch by upgrading to MySQL Server version 8.0.33 or later. The official security advisory with detailed patch information is available from Oracle April 2023 Security Alerts. Additional information regarding affected NetApp products can be found in the NetApp Security Advisory NTAP-20230427-0007.
Workarounds
- Restrict network access to MySQL Server to trusted hosts only using firewall rules
- Implement strict access controls to limit the number of high-privileged accounts
- Monitor and audit all administrative access to MySQL Server instances
- Consider network segmentation to isolate database servers from untrusted networks
# Example: Restrict MySQL network access using iptables
# Allow MySQL connections only from trusted application servers
iptables -A INPUT -p tcp --dport 3306 -s 10.0.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 3306 -j DROP
# Verify MySQL version after patching
mysql --version
# Expected: mysql Ver 8.0.33 or later
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
