CVE-2025-21559 Overview
CVE-2025-21559 is a vulnerability in the MySQL Server product of Oracle MySQL, specifically affecting the InnoDB storage engine component. This security flaw allows a high-privileged attacker with network access to compromise MySQL Server through multiple protocols. The vulnerability is considered easily exploitable and can result in a complete denial of service (DoS) condition, causing the MySQL Server to hang or repeatedly crash. Additionally, successful exploitation enables unauthorized modification of accessible MySQL Server data.
Critical Impact
High-privileged attackers can cause complete denial of service of MySQL Server and perform unauthorized data modifications through the InnoDB component.
Affected Products
- Oracle MySQL Server 8.0.40 and prior versions
- Oracle MySQL Server 8.4.3 and prior versions
- Oracle MySQL Server 9.1.0 and prior versions
Discovery Timeline
- 2025-01-21 - CVE-2025-21559 published to NVD
- 2025-11-03 - Last updated in NVD database
Technical Details for CVE-2025-21559
Vulnerability Analysis
This vulnerability resides in the InnoDB storage engine, which is the default and most commonly used storage engine for MySQL. The flaw is classified under CWE-306 (Missing Authentication for Critical Function), indicating that certain critical operations within the InnoDB component lack proper authentication controls.
The vulnerability requires high privileges to exploit but offers a low attack complexity once those privileges are obtained. An attacker with administrative or elevated access to the MySQL Server can leverage this flaw through network-accessible protocols to trigger denial of service conditions and modify database contents without proper authorization checks.
Root Cause
The root cause of CVE-2025-21559 stems from missing authentication for critical functions within the InnoDB storage engine. This architectural weakness allows authenticated high-privileged users to perform operations that bypass normal security constraints, leading to both availability and integrity impacts on the MySQL Server.
Attack Vector
The attack vector is network-based, meaning an attacker must have network access to the MySQL Server instance. The exploitation requires:
- High-privileged access to the MySQL Server (such as administrative credentials)
- Network connectivity to the target MySQL instance
- The ability to send specially crafted requests through supported MySQL protocols
Once these prerequisites are met, the attacker can trigger operations within the InnoDB engine that cause the server to hang or crash repeatedly, effectively denying service to legitimate users. The attacker can also perform unauthorized insert, update, or delete operations on accessible data.
The vulnerability does not require user interaction and the scope remains unchanged, meaning the impact is contained within the vulnerable MySQL Server instance.
Detection Methods for CVE-2025-21559
Indicators of Compromise
- Unexpected MySQL Server crashes or hangs, particularly recurring instances without clear system resource exhaustion
- Unusual administrative connection patterns or authentication events from unexpected network sources
- Database modification logs showing unauthorized changes to data during periods of service disruption
- InnoDB-specific error messages in MySQL error logs preceding server crashes
Detection Strategies
- Monitor MySQL error logs for InnoDB-related crashes and unexpected shutdowns using centralized log aggregation
- Implement database activity monitoring (DAM) solutions to track high-privileged user operations and detect anomalous patterns
- Deploy network intrusion detection systems (NIDS) to identify unusual MySQL protocol traffic patterns
- Configure alerting for repeated MySQL service restarts or availability interruptions
Monitoring Recommendations
- Enable and centralize MySQL general query logs and slow query logs for forensic analysis capability
- Implement real-time monitoring of MySQL process health and automatic alerting on service failures
- Track privileged account usage patterns and establish baselines to detect deviation
- Monitor InnoDB-specific performance counters and status variables for anomalies preceding crashes
How to Mitigate CVE-2025-21559
Immediate Actions Required
- Apply the Oracle Critical Patch Update from January 2025 immediately to affected MySQL Server installations
- Review and restrict high-privileged account access to only essential personnel and systems
- Implement network segmentation to limit direct access to MySQL Server instances
- Enable comprehensive logging and monitoring on all MySQL Server deployments
Patch Information
Oracle has addressed this vulnerability in the January 2025 Critical Patch Update. Administrators should upgrade affected MySQL Server installations to the following patched versions:
- MySQL Server 8.0.x: Upgrade to version 8.0.41 or later
- MySQL Server 8.4.x: Upgrade to version 8.4.4 or later
- MySQL Server 9.1.x: Upgrade to version 9.1.1 or later
Detailed patch information and download links are available in the Oracle Critical Patch Update January 2025. Organizations using NetApp products that bundle MySQL should also consult the NetApp Security Advisory NTAP-20250131-0004 for guidance.
Workarounds
- Restrict network access to MySQL Server by implementing firewall rules that limit connections to trusted IP addresses only
- Apply the principle of least privilege by reviewing and reducing the number of accounts with high-privilege access
- Consider placing MySQL Server instances behind a database proxy or firewall that can provide additional authentication layers
- Implement database activity monitoring to detect and alert on suspicious high-privileged operations while awaiting patch deployment
# Configuration example - Restrict MySQL network access via iptables
# Allow MySQL connections only from trusted application servers
iptables -A INPUT -p tcp --dport 3306 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 3306 -j DROP
# Alternatively, bind MySQL to localhost only in my.cnf if remote access is not required
# [mysqld]
# bind-address = 127.0.0.1
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
