MySQL2: Auth Plugin Downgrade to mysql_clear_password Leaks Plaintext Credentials

Summary

A rogue MySQL server (or MITM) can force mysql2 to send credentials in plaintext by requesting an auth switch to mysql_clear_password. The driver complies without verifying that TLS is active.

Details

mysql_clear_password is registered as a default standard plugin in lib/commands/auth_switch.js (line 21). When a server sends an AuthSwitchRequest (0xFE) requesting mysql_clear_password, the driver executes it without checking for TLS. The plugin (lib/auth_plugins/mysql_clear_password.js) returns Buffer.from(password + '\0').

Note: caching_sha2_password plugin DOES check for SSL before sending cleartext (line 77). But mysql_clear_password has no such guard.

Attack Scenario

1. Attacker operates rogue MySQL server or performs MITM 2. Server advertises caching_sha2_password in handshake 3. Client sends hashed auth response 4. Server replies with AuthSwitchRequest to mysql_clear_password 5. Client sends password in plaintext 6. Attacker captures plaintext password

PoC

Rogue MySQL server (Node.js, ~80 lines) that captures plaintext passwords from mysql2 clients. Tested against mysql2 3.20.0. Full PoC available on request.

Suggested Fix

Remove mysql_clear_password from standardAuthPlugins, or add a guard requiring TLS/unix socket before allowing cleartext auth.

Impact

• mysql2: 9M weekly downloads
• Any application connecting without TLS is vulnerable to credential theft
• Cloud environments with untrusted network paths are especially at risk