CVE-2025-21490: Oracle MySQL Server DoS Vulnerability

CVE-2025-21490 Overview

CVE-2025-21490 is a resource exhaustion vulnerability in the InnoDB storage engine component of Oracle MySQL Server. This vulnerability allows a high-privileged attacker with network access to cause a complete denial of service condition, resulting in a hang or frequently repeatable crash of the MySQL Server instance. The vulnerability is classified as CWE-770 (Allocation of Resources Without Limits or Throttling), indicating improper resource management within the InnoDB component.

Critical Impact

Successful exploitation enables authenticated attackers with administrative privileges to completely disrupt MySQL database availability through repeatable crashes or system hangs, potentially affecting all dependent applications and services.

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
• Debian Linux 11.0 (via MySQL packages)

Discovery Timeline

• 2025-01-21 - CVE-2025-21490 published to NVD
• 2025-11-03 - Last updated in NVD database

Technical Details for CVE-2025-21490

Vulnerability Analysis

This vulnerability resides in the InnoDB storage engine, MySQL's default transactional storage engine responsible for ACID-compliant data management. The flaw involves improper allocation of resources without appropriate limits or throttling mechanisms (CWE-770), which can be triggered by a privileged attacker through network-accessible protocols.

The attack requires high privileges (such as database administrator access) but has low attack complexity, meaning once an attacker has obtained the necessary access level, exploitation is straightforward. The vulnerability exclusively impacts availability—there are no confidentiality or integrity impacts, as the attacker cannot read or modify data through this vulnerability.

Root Cause

The root cause stems from inadequate resource management within the InnoDB component. When specific operations are performed, the storage engine fails to properly limit or throttle resource allocation, allowing an attacker to exhaust system resources and trigger a denial of service condition. This resource exhaustion can manifest as either a complete system hang or a repeatable crash of the MySQL Server process.

Attack Vector

The attack vector is network-based, allowing exploitation via multiple MySQL communication protocols. An attacker must first authenticate with high-level privileges (such as SUPER, SYSTEM_VARIABLES_ADMIN, or equivalent administrative permissions) before triggering the vulnerable code path in the InnoDB engine.

The exploitation scenario involves:

1. Attacker establishes authenticated network connection to MySQL Server
2. Attacker uses administrative privileges to execute specific InnoDB operations
3. The vulnerable resource allocation code is triggered without proper throttling
4. MySQL Server enters a hung state or crashes repeatedly

Due to the nature of this vulnerability, exploitation does not involve traditional code injection. The attack leverages legitimate administrative operations to trigger the resource exhaustion condition within InnoDB. For detailed technical information, refer to the Oracle Critical Patch Update Advisory.

Detection Methods for CVE-2025-21490

Indicators of Compromise

• Unexpected MySQL Server process crashes or restarts in system logs
• High resource consumption (memory, CPU) by the mysqld process preceding crashes
• InnoDB-related error messages in MySQL error logs indicating resource allocation failures
• Repeated authentication events from administrative accounts followed by service disruptions

Detection Strategies

• Monitor MySQL error logs for InnoDB-specific crash signatures and resource exhaustion errors
• Implement alerting on unexpected MySQL service restarts or process terminations
• Track administrative authentication events and correlate with subsequent service anomalies
• Deploy database activity monitoring (DAM) solutions to audit high-privilege operations

Monitoring Recommendations

• Enable MySQL General Query Log or Audit Log plugin for administrative session tracking
• Configure system resource monitoring with alerts for mysqld memory and CPU thresholds
• Implement automated MySQL health checks to detect hung or unresponsive database states
• Review InnoDB status output (SHOW ENGINE INNODB STATUS) for anomalous resource patterns

How to Mitigate CVE-2025-21490

Immediate Actions Required

• Update MySQL Server to patched versions as specified in Oracle's January 2025 Critical Patch Update
• Review and restrict high-privilege database accounts to minimize attack surface
• Implement network segmentation to limit MySQL Server access to trusted hosts only
• Enable MySQL audit logging to track administrative operations

Patch Information

Oracle has addressed this vulnerability in the January 2025 Critical Patch Update. Administrators should upgrade to the following minimum versions:

• MySQL 8.0.x: Upgrade to version 8.0.41 or later
• MySQL 8.4.x: Upgrade to version 8.4.4 or later
• MySQL 9.1.x: Upgrade to version 9.1.1 or later

For Debian Linux users, consult the Debian LTS Announcement for package updates. NetApp customers should reference the NetApp Security Advisory for appliance-specific guidance.

Workarounds

• Restrict administrative database privileges using the principle of least privilege
• Implement network-level access controls (firewall rules, security groups) to limit MySQL connectivity
• Configure MySQL to bind only to trusted network interfaces rather than all interfaces
• Enable connection rate limiting and resource quotas where supported

# Configuration example - Restrict MySQL network binding and enable audit logging
# Add to my.cnf or my.ini under [mysqld] section

# Bind MySQL to specific trusted interface only
bind-address = 127.0.0.1

# Limit maximum connections to prevent resource exhaustion
max_connections = 100

# Enable general query log for administrative session auditing
general_log = 1
general_log_file = /var/log/mysql/mysql-general.log

# Restart MySQL service after configuration changes
# systemctl restart mysql