CVE-2026-45712 Mailpit: Concurrent map read & write in proxy CSS rewriter - remote unauth crash (fatal error: concurrent map read and map write)

Mailpit is an email testing tool and API for developers. Prior to version 1.30.0, the screenshot/print proxy /proxy?data=… maintains a package-level assets mapstringMessageAssets cache, but reads the map without holding assetsMutex while a long-running cleanup goroutine and re-entrant CSS-rewriti...