EC
1649
MySQLERRORNotableAccess ControlHIGH confidence

GRANT would create a new account but user already exists with a different plugin

Production Risk

Low — the GRANT is rejected; no privilege change occurs.

What this means

A GRANT statement tried to create a user implicitly, but a user with that name already exists and is configured with a different authentication plugin.

Why it happens
  1. 1The user already exists with a specific authentication plugin, and the GRANT statement specifies a different plugin or no plugin.
How to reproduce
trigger — this will error
trigger — this will error
GRANT SELECT ON db.* TO 'user'@'%' IDENTIFIED WITH caching_sha2_password BY 'pass';

expected output

ERROR 1649 (HY000): Account already exists with a different authentication plugin.

Fix

Use ALTER USER to change the authentication plugin separately

Use ALTER USER to change the authentication plugin separately
ALTER USER 'user'@'%' IDENTIFIED WITH caching_sha2_password BY 'pass';
GRANT SELECT ON db.* TO 'user'@'%';

Why this works

Separating user modification from grant avoids implicit user creation conflicts.

Version notes

Sources
Official documentation ↗

MySQL 8.0 — 1649 ER_GRANT_PLUGIN_USER_EXISTS

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