GHSA-3x6r-wxxg-53vv

## 1. Summary A transport failure during the initial Infinite Scale TUS creation POST can return `(nil response, non-nil error)`. Rclone dereferences the nil response before processing the error and panics. The production `CreateUploader` path reproduced the crash against a closed endpoint. The security case is deployment-dependent. A one-shot upload already fails when its endpoint resets, while RC jobs recover panics in `fs/rc/jobs/job.go` and return a job error. The incremental denial of service is strongest in a long-lived VFS mount or concurrent/multi-remote CLI process where the upload runs in an unrecovered goroutine and the panic terminates unrelated work. ## 2. Affected Assets & Attack Surface - Verified rclone revision: `a0c09f1381ae93e2a9a33c529d170186c61ad058` (`v1.74.0-240-ga0c09f138`) - Current-master check: `backend/webdav/tus.go` was unchanged at master commit `961266888fe797390c535386f3b3aa46f4853602` on 2026-07-18 - Response evaluation: `backend/webdav/tus.go:45-59` - Creation path: `backend/webdav/tus.go:61-107` - Unrecovered VFS caller: `vfs/write.go:71-81` - Contained RC caller: `fs/rc/jobs/job.go:107-115` - Configuration: Infinite Scale WebDAV uploads using TUS - Code triggers: any pre-response transport failure, including refusal, reset, timeout, DNS/TLS/proxy failure, or cancellation - Security trigger: a malicious/compromised configured endpoint resets an upload in a long-lived or multi-workload process ## 3. Technical Root Cause Analysis `getTusLocationOrRetry` switches on `resp.StatusCode` before checking whether `resp` is nil or handling the accompanying error. A nil response is valid when the HTTP transaction fails before a response is parsed. There is no recovery boundary in the WebDAV operation itself. Whether the panic is process-fatal depends on its caller: the VFS write path starts `operations.Rcat` in an unrecovered goroutine (`vfs/write.go:71-81`), whereas RC jobs wrap their function in `recover` (`fs/rc/jobs/job.go:107-115`)