CVE-2026-91937

Flowise before version 3.1.4 does not sanitize the overrideConfig.sessionId parameter before passing it to MongoDB queries inside the MongoDBMemory node, allowing a NoSQL injection (CWE-943). An unauthenticated attacker can send MongoDB operator objects (such as $ne or $regex constructs) as the sessionId value through the publicly reachable prediction API (/api/v1/prediction) to manipulate the query filter. Successful injection lets the attacker read chat history records belonging to other users stored in the shared MongoDB collection, exposing potentially sensitive conversation content without any authentication. Deployments are only vulnerable if they use the MongoDBMemory node and expose the prediction endpoint, with self-hosted instances that lack an auth layer in front of the API at greatest risk. No public proof of concept exists and no exploitation in the wild has been observed as of this analysis.

What to do: Upgrade Flowise to version 3.1.4 or later, which sanitizes the sessionId parameter before it reaches MongoDB. If immediate patching is not possible, place authentication or an IP-restricting reverse proxy in front of the /api/v1/prediction endpoints, and review chat-history collections for evidence of NoSQL operator payloads in session IDs indicating probing or data access.