CVE-2026-42862: Flowise: Mass Assignment in Tool Update Endpoint Allows Cross-Workspace Resource Reassignment

Synopsis

A mass assignment vulnerability in the Flowise tool update endpoint allows an authenticated user to overwrite server-controlled fields, including workspaceId, when submitting a tool update request. The attack is reachable over the network with a low-privilege account and no victim interaction, though it requires meeting certain environmental conditions reflected in the high attack complexity rating. Successful exploitation breaks tenant isolation in multi-workspace deployments by reassigning tools to arbitrary workspaces, enabling cross-workspace data access and content tampering. HarborGuard tracks this advisory and will make a patched-image rebuild available at version 3.1.2 the moment the upstream fix is confirmed and published.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityRequired

  The vulnerable endpoint is exposed over the network, so the attacker must be able to reach the Flowise service via HTTP.

• AuthenticationRequired

  Any low-privilege authenticated account is sufficient; no administrative credentials are needed to send a crafted tool update request.

• Victim interactionNot required

  The attacker sends a malformed API request directly; no action from another user or administrator is needed.

• Attack complexityDetail

  The CVSS v4.0 vector rates attack complexity as high, indicating the attacker must satisfy specific environmental or timing conditions beyond simply sending the request.

Blast Radius

• Reads tool definitions and associated configuration data belonging to other workspaces in a multi-tenant Flowise deployment.
• Reassigns tools across workspace boundaries, corrupting tenant isolation and exposing one workspace's LLM flow assets to another.
• Modifies server-controlled metadata fields (workspaceId, createdDate, updatedDate) on tool records without authorization.