Leapp-repository: leapp-upgrade-el9toel10: leapp-upgrade-el9toel10: scan_mysql runs mysqld --validate-config as root and can load mysql-writable plugins

A privilege escalation flaw was found in the scan_mysql actor of leapp-upgrade-el9toel10 (provided by leapp-repository). During RHEL 9 to RHEL 10 upgrades, the actor runs:
mysqld --validate-config --log-error-verbosity=2 directly as root in the Leapp actor context, bypassing the packaged MySQL systemd unit that normally starts the daemon as User=mysql.

A process compromised as the mysql OS identity can write a version-2 persisted configuration (mysqld-auto.cnf) and a malicious shared object into /var/lib/mysql (a directory owned by mysql). That persisted map can set plugin_dir to /var/lib/mysql and early_plugin_load (or related loader options such as plugin_load / plugin_load_add) so MySQL loads the attacker-controlled object during configuration validation. Plugin loading can reach dlopen() before MySQL’s runtime-user check and before plugin-symbol validation.

When an administrator subsequently runs the documented Leapp preupgrade or upgrade workflow, attacker-controlled code can execute as UID 0 with a full capability set in an unconfined SELinux domain (unconfined_t). The attack does not require write access to the default system plugin path under /usr; redirecting plugin_dir via mysql-owned persisted state is sufficient. Ordinary SQL privileges alone (including highly privileged SQL accounts) are not a sufficient startpoint — OS-level execution as the mysql service identity is required, plus later administrator invocation of Leapp.