CVE-2026-55429: Coder's workspace app upsert allows cross-workspace agent rebinding via user-controlled app ID

UpsertWorkspaceApp overwrites an existing app’s agent_id on a primary-key conflict and insertAgentApp accepts the app ID from the provisioner’s CompleteJob payload without verifying it belongs to the workspace being built. CompleteJob runs under dbauthz.AsProvisionerd so the authorization layer does not block the cross-workspace upsert.

Note: Exploitation requires elevated access as a template author or external provisioner operator.