CVE-2025-21522
📋 TL;DR
A vulnerability in MySQL Server's parser component allows authenticated attackers with network access to cause denial of service by crashing or hanging the server. This affects MySQL 8.0.40 and earlier, 8.4.3 and earlier, and 9.1.0 and earlier versions. Attackers need only low privileges to exploit this vulnerability.
💻 Affected Systems
- Oracle MySQL Server
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete unavailability of MySQL Server leading to application downtime and service disruption
Likely Case
Intermittent service outages and performance degradation affecting dependent applications
If Mitigated
Limited impact with proper network segmentation and privilege restrictions
🎯 Exploit Status
Oracle describes as 'easily exploitable' but requires authenticated access with low privileges
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Apply Critical Patch Update for January 2025 or later
Vendor Advisory: https://www.oracle.com/security-alerts/cpujan2025.html
Restart Required: Yes
Instructions:
1. Download the appropriate Critical Patch Update from Oracle
2. Apply the patch following Oracle's documentation
3. Restart MySQL service to apply changes
🔧 Temporary Workarounds
Network Access Restriction
allRestrict network access to MySQL Server to only trusted hosts
# In my.cnf/my.ini: bind-address = 127.0.0.1
# Or use firewall: iptables -A INPUT -p tcp --dport 3306 -s trusted_ip -j ACCEPT
Privilege Reduction
allReview and minimize low-privileged user accounts and their permissions
REVOKE ALL PRIVILEGES ON *.* FROM 'lowprivuser'@'%';
DROP USER 'unnecessaryuser'@'%';
🧯 If You Can't Patch
- Implement strict network segmentation to isolate MySQL servers from untrusted networks
- Regularly monitor for unusual connection patterns or repeated crashes in MySQL logs
🔍 How to Verify
Check if Vulnerable:
Check MySQL version and compare against affected versions: SELECT VERSION();Check Version:
mysql --version OR SELECT VERSION();Verify Fix Applied:
Verify version is updated beyond affected ranges and check patch application logs📡 Detection & Monitoring
Log Indicators:
- Unexpected MySQL crashes or restarts
- Multiple connection attempts from single low-privileged accounts
- Parser-related error messages in MySQL error log
Network Indicators:
- Unusual traffic patterns to MySQL port 3306 from unexpected sources
- Multiple rapid connections followed by service unavailability
SIEM Query:
source="mysql_error.log" AND ("crash" OR "shutdown" OR "parser")