MySQL

A MySQL server reachable on the network is a direct line to whatever the application stores — users, password hashes, session data, business records. Weak or reused credentials get you in, and from there secure_file_priv and FILE privileges can turn a database login into file reads and sometimes code execution.

What Is MySQL?

MySQL is an open-source relational database management system, developed and supported by Oracle. Databases are often dumped to a single .sql file (e.g. wordpress.sql).

A MySQL server translates SQL commands into executable actions and returns the result to the client — a table extract, login records, search results, and so on. When something goes wrong during processing, the application reports an error, and those errors are exactly what SQL injection provokes to manipulate the database.

Default Configuration

MySQL is configured through /etc/mysql/mysql.conf.d/mysqld.cnf (or my.cnf):

# mysqld.cnf
[mysqld]
user            = mysql
pid-file        = /var/run/mysqld/mysqld.pid
socket          = /var/run/mysqld/mysqld.sock
port            = 3306
bind-address    = 127.0.0.1

Dangerous Settings

The security-relevant options:

Setting	Risk
`user`	The OS user MySQL runs as — stored in plain text in the config
`password`	The MySQL user's password — plain text in the config
`admin_address`	IP for TCP/IP connections on the admin interface
`debug`	Current debugging settings — verbose error output
`sql_warnings`	Whether single-row INSERTs produce info strings on warnings
`secure_file_priv`	Limits import/export operations — if empty, enables arbitrary file read/write

user, password, and admin_address matter because they're stored in plain text. Config-file permissions are often set wrong — so if you get any file-read primitive or a shell, you can read the MySQL username and password straight out of the config.

debug and sql_warnings produce verbose error output. That's useful to an administrator but leaks sensitive content to everyone else — error messages are often shown directly in the web application, and that detail can be used to refine SQL injection, sometimes to the point of getting the server to execute system commands.

Footprinting the Service

Nmap

MySQL runs on TCP 3306. Scan with the MySQL NSE scripts:

nmap -sV -sC -p3306 --script mysql-* 10.129.14.128

PORT     STATE SERVICE VERSION
3306/tcp open  mysql   MySQL 8.0.27
| mysql-info:
|   Protocol: 10
|   Version: 8.0.27
|   Capabilities flags: 65535
|_  Auth Plugin Name: caching_sha2_password
| mysql-empty-password:
|_  root account has empty password

Connecting

mysql -u root -p'Password123' -h 10.129.14.128

Enumerating Databases

Once in, list the databases. Two always exist and matter for orientation:

SHOW DATABASES;

+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
| wordpress          |
+--------------------+

information_schema — metadata about every database, table, and column on the server
sys — system schema with tables, info, and metadata for management

The application's own database (wordpress here) is where the interesting data lives — users and password hashes especially.

MySQL Command Reference

Command	Purpose
`mysql -u <user> -p<password> -h <ip>`	Connect (no space after `-p`)
`SHOW DATABASES;`	List all databases
`USE <database>;`	Select a database
`SHOW TABLES;`	List tables in the selected database
`SHOW COLUMNS FROM <table>;`	List a table's columns
`SELECT * FROM <table>;`	Dump a table
`SELECT * FROM <table> WHERE <column> = "<string>";`	Search a table

A typical hunt — find the users table and pull credentials:

USE wordpress;
SHOW TABLES;
SELECT user_login, user_pass FROM wp_users;

+------------+------------------------------------+
| user_login | user_pass                          |
+------------+------------------------------------+
| admin      | $P$B7e3.x...hashed...               |
+------------+------------------------------------+

Quick Reference

Command	Purpose
`nmap -sV -sC -p3306 --script mysql-* <ip>`	Enumerate MySQL (confirm false positives)
`mysql -u <user> -p<pass> -h <ip>`	Connect
`SHOW DATABASES;` → `USE <db>;` → `SHOW TABLES;`	Explore structure
`SELECT * FROM <table>;`	Dump data
`SELECT LOAD_FILE('/etc/passwd');`	Read a file (needs FILE priv + empty `secure_file_priv`)

The footprinting flow: nmap for 3306 and version → confirm results manually → log in with found/guessed creds → enumerate databases → dump the application's user table → abuse FILE privileges if secure_file_priv is open.

Next: MSSQL — Microsoft SQL Server, xp_cmdshell, and command execution.