Flowise is a drag-and-drop interface for building customized large language model flows. In versions before 3.1.3, the unauthenticated POST /api/v1/prediction/:id endpoint accepted an overrideConfig object that was merged into internal flowConfig and flowData objects without verifying apiOverrideStatus. This lack of authorization checks enabled unauthenticated attackers to inject arbitrary properties into the flow execution context of any public chatflow, allowing them to overwrite critical values like chatId, sessionId, and chatHistory, and manipulate values resolved through $flow.* template variables used by flow nodes. The vulnerability is addressed in Flowise version 3.1.3.

An unauthenticated attacker can bypass authorization controls to inject arbitrary properties into the flow execution context, potentially manipulating session-related data and flow variables. This could lead to unauthorized control over flow execution and compromise the integrity of chat sessions. The CVSS 4.0 base score is 8.8 (high severity), reflecting network attack vector, no privileges required, no user interaction, and high impact on integrity and availability.

Upgrade Flowise to version 3.1.3 or later, where this vulnerability is fixed. There is no indication of alternative mitigations or temporary workarounds. Patch status is confirmed fixed in 3.1.3.