CVE-2026-5774: Juju: In-Memory Token Store for Discharge Tokens Lacks Concurrency Safety and Persistence

The localLoginHandlers struct in the Juju API server maintains an in-memory map to store discharge tokens following successful local authentication. This map is accessed concurrently from multiple HTTP handler goroutines without any synchronization primitive protecting it. The absence of a mutex or equivalent mechanism means that concurrent reads, writes, and deletes on the map can trigger Go runtime panics and may allow a discharge token to be consumed more than once before deletion completes.