CVE-2025-21543: Oracle MySQL Cluster DOS Vulnerability

CVE-2025-21543 Overview

CVE-2025-21543 is a Denial of Service (DoS) vulnerability affecting the Server: Packaging component of Oracle MySQL Server and MySQL Cluster. 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.

The vulnerability is classified as easily exploitable, requiring only network access via multiple protocols. While the attack requires high privileges, successful exploitation can completely disrupt database availability, making it a significant concern for organizations relying on MySQL for critical operations.

Critical Impact

Successful exploitation allows attackers to cause a complete denial of service (DoS) of the MySQL Server, resulting in service hangs or repeatedly crashing the database, potentially disrupting business operations dependent on MySQL availability.

Affected Products

• Oracle MySQL Server versions 8.0.40 and prior
• Oracle MySQL Server versions 8.4.3 and prior
• Oracle MySQL Server versions 9.1.0 and prior
• Oracle MySQL Cluster (corresponding affected versions)

Discovery Timeline

• 2025-01-21 - CVE CVE-2025-21543 published to NVD
• 2025-11-03 - Last updated in NVD database

Technical Details for CVE-2025-21543

Vulnerability Analysis

This vulnerability resides in the Server: Packaging component of Oracle MySQL Server. The flaw is associated with CWE-770 (Allocation of Resources Without Limits or Throttling), indicating that the vulnerability stems from improper resource management within the packaging component.

The vulnerability allows an authenticated attacker with high privileges and network access to trigger resource exhaustion or mishandling conditions within the MySQL Server's packaging component. When exploited, this leads to service disruption without affecting data confidentiality or integrity—the impact is purely on availability.

The attack can be conducted via multiple network protocols supported by MySQL, making it potentially accessible from various network entry points. Although high privileges are required, in environments where administrative access may be compromised or where insider threats exist, this vulnerability presents a tangible risk to service continuity.

Root Cause

The root cause of CVE-2025-21543 is related to CWE-770: Allocation of Resources Without Limits or Throttling. The MySQL Server's Packaging component fails to properly limit or throttle resource allocation during certain operations. This allows an attacker with sufficient privileges to trigger conditions that exhaust system resources or cause the server to enter an unstable state, resulting in a denial of service.

Attack Vector

The attack vector is network-based, allowing exploitation remotely. An attacker must possess high-level privileges on the MySQL Server to exploit this vulnerability. The attack can be conducted through multiple protocols that MySQL Server supports for network communication.

The attack does not require user interaction and the scope is unchanged, meaning the vulnerability's impact is confined to the MySQL Server component itself. The exploitation complexity is low, making it straightforward for an authenticated privileged attacker to trigger the denial of service condition.

Due to the nature of this vulnerability involving resource allocation issues in the packaging component, specific exploitation details are not publicly disclosed. Organizations should refer to the Oracle Security Alert January 2025 for detailed technical information about the vulnerability and remediation guidance.

Detection Methods for CVE-2025-21543

Indicators of Compromise

• Unexpected MySQL Server crashes or hangs occurring repeatedly
• Abnormal resource consumption (CPU, memory) by MySQL Server processes
• Authentication logs showing privileged account activity followed by service disruption
• Error logs indicating packaging component failures or resource exhaustion conditions

Detection Strategies

• Monitor MySQL Server availability and implement automated restart detection with alerting
• Audit privileged user activity and correlate with service stability metrics
• Implement anomaly detection for unusual database server resource consumption patterns
• Review MySQL error logs for signs of packaging component errors or crashes

Monitoring Recommendations

• Enable comprehensive MySQL Server logging including error logs and slow query logs
• Configure real-time alerting for MySQL Server process crashes or availability issues
• Monitor network connections to MySQL Server for unusual privileged session activity
• Implement database health monitoring dashboards to detect availability anomalies quickly

How to Mitigate CVE-2025-21543

Immediate Actions Required

• Apply the Oracle Critical Patch Update (CPU) from January 2025 immediately
• Review and audit all high-privilege MySQL user accounts and access permissions
• Implement network segmentation to limit who can access MySQL Server administrative interfaces
• Enable enhanced logging to detect potential exploitation attempts

Patch Information

Oracle has released a security patch addressing this vulnerability in the January 2025 Critical Patch Update. Organizations should upgrade their MySQL Server installations to the latest patched versions:

• Upgrade MySQL Server 8.0.40 and earlier to the patched 8.0.x release
• Upgrade MySQL Server 8.4.3 and earlier to the patched 8.4.x release
• Upgrade MySQL Server 9.1.0 and earlier to the patched 9.1.x release

Refer to the Oracle Security Alert January 2025 for specific patch download instructions and version numbers. Additional guidance may also be found in the NetApp Security Advisory NTAP-20250131-0004.

Workarounds

• Restrict network access to MySQL Server administrative interfaces using firewall rules
• Review and minimize the number of accounts with high-privilege MySQL access
• Implement connection rate limiting and resource quotas where possible
• Consider implementing high-availability configurations to minimize impact of potential DoS attacks

# Example: Restrict MySQL admin access to specific IP ranges using iptables
# Allow MySQL connections only from trusted management network
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 current MySQL user privileges
mysql -u root -p -e "SELECT user, host FROM mysql.user WHERE Super_priv='Y';"