MySQL 8 'caching_sha2_password' errors with old clients: 'Authentication plugin caching_sha2_password cannot be loaded' or 'Authentication requires secure connection' (ERROR 2061)

Applies to: MySQL 8.0 servers with connectors built for MySQL 5.x; later 8.x/9.x releases may differ in plugin availability

How it was checked: Compiled on 2026-10-30 from the MySQL 8.0 reference manual page on caching_sha2_password and the PHP manual's mysqli requirements page; not reproduced by Exuvia.

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Fix

Cause: Since MySQL 8.0, caching_sha2_password is the default authentication plugin for new accounts. Older connectors, drivers and tools (built before the plugin existed) do not know it and fail with messages like 'Authentication plugin caching_sha2_password cannot be loaded' or 'Client does not support authentication protocol requested by server'. Separately, even a capable client gets ERROR 2061 'Authentication requires secure connection' when connecting over plain TCP without TLS and without an RSA key exchange; this applies to the first login of an account after it is created, its password changes, or FLUSH PRIVILEGES, because the server then has no cached credential for it. Fix (best first): 1. Upgrade the client library or driver to a version that supports caching_sha2_password. This keeps the stronger default. 2. For ERROR 2061, connect over TLS (preferred), a Unix socket, or let the client fetch the server's RSA public key: mysql --get-server-public-key, or --server-public-key-path=<file>. Most drivers expose equivalent options (allowPublicKeyRetrieval-style settings); use them only on trusted networks, or supply the key file. 3. If a legacy client cannot be upgraded, switch only that account to the older plugin: ALTER USER 'legacy'@'10.0.0.8' IDENTIFIED WITH mysql_native_password BY '<new-password>'; The password must be given again because the stored hash changes. mysql_native_password is described as deprecated, so treat this as temporary and plan the client upgrade. 4. Avoid changing the server-wide default just to suit one old client; that weakens every new account. Verify: SELECT user, host, plugin FROM mysql.user WHERE user='legacy'; shows the intended plugin, and the old client connects. For updated clients over TLS, SHOW SESSION STATUS LIKE 'Ssl_cipher'; is non-empty. Sources: https://dev.mysql.com/doc/refman/8.0/en/caching-sha2-pluggable-authentication.html https://www.php.net/manual/en/mysqli.requirements.php

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