How CVE-2025-21536 Works
This vulnerability exists in MySQL Server’s optimizer component, affecting versions 8.0.39 and prior, 8.4.2 and prior, and 9.0.1 and prior. A high-privileged attacker with network access can exploit improper query optimization handling, causing the server to hang or crash repeatedly. The flaw triggers when specially crafted SQL queries force the optimizer into an infinite loop or resource exhaustion state, leading to a complete denial-of-service (DoS). The CVSS 3.1 score of 4.9 reflects its medium severity due to the requirement of high privileges (PR:H) but low attack complexity (AC:L).
DailyCVE Form
Platform: MySQL Server
Version: 8.0.39, 8.4.2, 9.0.1
Vulnerability: Optimizer DoS
Severity: Medium
Date: 04/08/2025
What Undercode Say:
Exploitation Analysis
1. Exploit Trigger: Malicious query forcing optimizer miscalculation
2. Impact: Complete MySQL service crash
3. Privilege Requirement: High (e.g., ‘SUPER’ privilege)
Detection Commands
SHOW VARIABLES LIKE '%version%'; -- Check vulnerable versions SELECT user, Super_priv FROM mysql.user WHERE Super_priv='Y'; -- Find high-priv users
Proof-of-Concept (PoC) Snippet
-- Hypothetical crash trigger (exact query withheld) SELECT FROM t1 JOIN t2 ON [bash];
Protection Measures
- Patch Immediately: Upgrade to MySQL 8.0.40+, 8.4.3+, or 9.0.2+
2. Access Control: Restrict SUPER privileges
REVOKE SUPER ON . FROM 'admin'@'%';
3. Query Filtering: Block complex joins via WAF rules
Log Monitoring
grep -i "optimizer" /var/log/mysql/error.log
Mitigation Script
!/bin/bash Checks for vulnerable MySQL versions mysql --version | grep -E "8.0.[0-39]|8.4.[0-2]|9.0.1" && echo "Vulnerable"
CVSS 4.0 Vector
`CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`
References
- Oracle Critical Patch Update Advisory (January 2025)
- MySQL 8.4.3 Release Notes (Fixed in Changelog)
References:
Reported By: https://nvd.nist.gov/vuln/detail/CVE-2025-21536
Extra Source Hub:
Undercode
