Had the same problem, solved this way:

I closed the jenkins url as this makes it usable but everybody becomes admin

Backed up the config.xml as it will be blanked out.

In $JENKINS_HOME/config.xml commented out/removed all the authorizationStrategy block and changed true to false.

Started jenkins (it started back normally but without authentication.

Changed the config.xml to previous original version (included all security previously running) and worked back normally with the original role strategy configuration in place.

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