How CVE-2025-21555 Works
This vulnerability exists in the InnoDB storage engine of MySQL Server (versions 8.0.40 and prior, 8.4.3 and prior, and 9.1.0 and prior). A high-privileged attacker with network access can exploit it via multiple protocols. The flaw occurs due to improper handling of certain InnoDB operations, leading to a race condition during transaction processing. When maliciously triggered, it causes a database hang or crash (DoS) by corrupting internal data structures. The attacker can also manipulate some database records, affecting integrity. The CVSS 3.1 score reflects medium severity due to the requirement of high privileges (PR:H) but significant availability impact (A:H).
DailyCVE Form:
Platform: MySQL Server
Version: 8.0.40, 8.4.3, 9.1.0 (and prior)
Vulnerability: InnoDB DoS
Severity: Medium
Date: 04/08/2025
What Undercode Say:
Exploitation Analysis:
1. Triggering the Crash:
- The attacker sends crafted transaction requests to overload InnoDB’s lock management system.
- Example malicious query:
BEGIN; SELECT FROM sensitive_table FOR UPDATE; -- Repeatedly execute conflicting transactions
2. Exploit Code (Python PoC):
import mysql.connector
def exploit_mysql(target_ip, user, password):
conn = mysql.connector.connect(host=target_ip, user=user, password=password)
cursor = conn.cursor()
cursor.execute("BEGIN; SELECT FROM mysql.user FOR UPDATE;")
Concurrently execute conflicting transactions
Protection Measures:
- Patch: Upgrade to MySQL versions beyond 8.0.40, 8.4.3, or 9.1.0.
2. Mitigation: Restrict high-privileged network access using:
REVOKE ALL PRIVILEGES ON . FROM 'admin'@'%';
3. Detection: Monitor logs for abnormal transaction patterns:
grep -i "deadlock" /var/log/mysql/error.log
Analytics:
- Attack Vector: Network (AV:N)
- Privilege Required: High (PR:H)
- Impact: Integrity (I:L), Availability (A:H)
References:
- Oracle Critical Patch Update Advisory (January 2025)
- NVD Entry: CVE-2025-21555
References:
Reported By: https://nvd.nist.gov/vuln/detail/CVE-2025-21555
Extra Source Hub:
Undercode
