CVE-2026-44552: Open WebUI: Redis Cache Keys tool_servers and terminal_servers Missing Instance Prefix Enable Cross-Instance Cache Poisoning

Open WebUI uses a REDIS_KEY_PREFIX (default open-webui) to namespace Redis keys, allowing multiple instances to safely share a single Redis backend. Every Redis key in the codebase uses this prefix — except the tool_servers and terminal_servers keys in utils/tools.py, which use bare key names.

When two or more Open WebUI instances share a Redis database (a supported and documented deployment pattern, e.g., for multi-region deployments, blue-green setups, or cluster topologies), the unprefixed keys collide. An admin on Instance A writing to tool_servers overwrites the value read by Instance B — causing Instance B’s users to receive Instance A’s tool server configuration.