Arcane: delegated users:update permission lets any operator reset the global administrator password

Impact

UpdateUser set PasswordHash for any target without comparing the caller's privilege to the target's, so a holder of the delegated users:update permission can change the global administrator's password and then log in as that account. Arcane manages Docker containers, images, networks and volumes, so global administrator there means full control of the container host behind it - launching privileged containers, mounting host paths, reading every image and volume. On a fleet where Arcane fronts GPU hosts, a junior operator account with user-management rights becomes root on those hosts, and the audit trail shows an administrator login rather than the escalation. Fixed in 2.6.0.

Who can reach it

An authenticated Arcane user holding the delegated users:update permission, over the network to the Arcane backend API. No administrator credentials needed; exposure is limited to whoever can authenticate and holds that permission.

What to do

Upgrade Arcane to backend v2.6.0 or later and restart the service - a container image bump and daemon restart, no host maintenance. Afterwards rotate the global administrator password and review user records for unexpected password changes, since the flaw leaves a usable administrator credential behind. Until the upgrade, revoke users:update from every account that does not need it.

References

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