CVE-2025-21522: Oracle MySQL Server DoS Vulnerability

CVE-2025-21522 Overview

CVE-2025-21522 is a denial of service vulnerability in the MySQL Server product of Oracle MySQL, specifically affecting the Server: Parser component. This vulnerability allows a low-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 under CWE-770 (Allocation of Resources Without Limits or Throttling), indicating that the parser component fails to properly limit resource consumption during certain operations. This flaw is easily exploitable via multiple network protocols, making it a significant availability concern for organizations running affected MySQL Server versions.

Critical Impact

Successful exploitation allows authenticated attackers to cause complete denial of service of MySQL Server instances, potentially disrupting critical database operations and dependent applications.

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-2025-21522 published to NVD
• 2025-11-03 - Last updated in NVD database

Technical Details for CVE-2025-21522

Vulnerability Analysis

This vulnerability resides in the Server: Parser component of Oracle MySQL Server. The parser is responsible for interpreting and processing SQL queries before execution. The flaw stems from improper resource allocation handling during query parsing, where specific input patterns can trigger excessive resource consumption.

An authenticated attacker with low privileges can craft malicious SQL queries that exploit the parser's resource handling weakness. When processed, these queries cause the server to enter a hung state or crash repeatedly, denying service to legitimate users and applications.

The vulnerability affects availability only—there is no impact on confidentiality or integrity of data. However, the ease of exploitation and the potential for repeated crashes make this a significant operational risk for production database environments.

Root Cause

The root cause is identified as CWE-770: Allocation of Resources Without Limits or Throttling. The MySQL Server Parser component fails to implement proper bounds checking or resource limits when processing certain query structures. This allows an attacker to submit queries that consume excessive server resources, ultimately leading to service disruption.

The parser's inability to handle malformed or specially crafted input gracefully results in a denial of service condition that persists until the malicious queries are stopped or the server is restarted.

Attack Vector

The attack vector is network-based and requires only low-privilege authentication to execute. An attacker can exploit this vulnerability through multiple protocols supported by MySQL Server. The attack does not require user interaction and can be launched remotely by any authenticated user with basic database access.

The attack flow involves:

1. An attacker establishes an authenticated connection to the MySQL Server
2. Specially crafted SQL queries are submitted to the parser component
3. The parser fails to properly limit resource allocation during query processing
4. The server enters a hung state or crashes, denying service to all users

Since no code examples are available from verified sources, organizations should consult the Oracle Critical Patch Update January 2025 for detailed technical information about the vulnerability mechanism and exploitation scenarios.

Detection Methods for CVE-2025-21522

Indicators of Compromise

• Unexpected MySQL Server crashes or hangs without apparent cause
• Elevated resource consumption (CPU, memory) during query parsing operations
• Repeated connection failures from legitimate applications
• Error logs showing parser-related exceptions or resource exhaustion messages

Detection Strategies

• Monitor MySQL error logs for frequent crash events or parser-related errors
• Implement query auditing to identify unusual or malformed SQL statements
• Track authentication events to identify potential attack sources
• Configure alerting for MySQL service availability and restart events

Monitoring Recommendations

• Enable MySQL slow query logging and analyze for anomalous query patterns
• Deploy database activity monitoring to track all authenticated sessions
• Set up automated health checks for MySQL Server availability
• Monitor system resource utilization for MySQL processes to detect resource exhaustion attacks

How to Mitigate CVE-2025-21522

Immediate Actions Required

• Apply the security patches provided in Oracle Critical Patch Update January 2025
• Audit database user accounts and revoke unnecessary privileges
• Implement network segmentation to restrict MySQL Server access to trusted hosts
• Enable enhanced logging and monitoring for MySQL Server instances

Patch Information

Oracle has released security patches addressing this vulnerability in the January 2025 Critical Patch Update. Organizations should upgrade to the following patched versions:

• MySQL Server versions newer than 8.0.40
• MySQL Server versions newer than 8.4.3
• MySQL Server versions newer than 9.1.0

For detailed patch information and download instructions, refer to the Oracle Critical Patch Update January 2025. Additional guidance is available in the NetApp Security Advisory NTAP-20250131-0004.

Workarounds

• Restrict network access to MySQL Server to trusted IP addresses only
• Implement strict firewall rules to limit exposure of database ports
• Review and minimize database user privileges following the principle of least privilege
• Consider deploying a database firewall or proxy to filter malicious queries

# Example: Restrict MySQL access to specific hosts using iptables
iptables -A INPUT -p tcp --dport 3306 -s trusted_network/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 3306 -j DROP

# Example: Review and audit MySQL user privileges
mysql -e "SELECT user, host, authentication_string FROM mysql.user;"