CVE-2026-42861: Flowiseai Flowise Auth Bypass Vulnerability

CVE-2026-42861 Overview

CVE-2026-42861 is a mass assignment vulnerability affecting FlowiseAI Flowise, a drag-and-drop user interface for building customized large language model (LLM) flows. The flaw exists in the variable update endpoint prior to version 3.1.2. Authenticated users can modify server-controlled properties including workspaceId, createdDate, and updatedDate when updating a variable resource. The endpoint lacks server-side validation and authorization checks on these fields. An attacker can manipulate the workspaceId field to reassign variables to arbitrary workspaces. This behavior breaks tenant isolation in multi-workspace deployments. The vulnerability is tracked under [CWE-284: Improper Access Control].

Critical Impact
Authenticated attackers can break tenant isolation in multi-workspace Flowise environments by reassigning variables across workspaces through unvalidated mass assignment.

Affected Products

FlowiseAI Flowise versions prior to 3.1.2
Multi-workspace Flowise deployments with multiple authenticated tenants
Self-hosted Flowise instances exposing the variable update API

Discovery Timeline

2026-06-08 - CVE-2026-42861 published to NVD
2026-06-11 - Last updated in NVD database

Technical Details for CVE-2026-42861

Vulnerability Analysis

The vulnerability stems from a mass assignment flaw in the Flowise variable update endpoint. Mass assignment occurs when an application binds user-supplied input directly to internal object properties without filtering. In this case, the endpoint accepts arbitrary fields from request payloads and writes them to the variable record. Server-managed fields such as workspaceId, createdDate, and updatedDate are not protected from client modification. An authenticated user who submits a crafted update request can overwrite the workspaceId of a variable. The variable is then moved into a workspace that the attacker controls or targets. This collapses the boundary between tenants that Flowise establishes through its workspace model.

Root Cause

The root cause is missing server-side validation and authorization on the variable update handler. The endpoint trusts the request body for all properties of the variable resource. There is no allowlist of mutable fields, and no check confirms the requesting user owns the destination workspace.

Attack Vector

Exploitation requires a valid authenticated session and network access to the Flowise API. The attacker sends an update request to the variable endpoint and includes the workspaceId field in the JSON body. The server applies the supplied value without verifying the user's authorization for the target workspace. Refer to the GitHub Security Advisory GHSA-6fw7-3q8r-m5vj for additional technical context.

// No verified exploit code is published.
// See the vendor advisory for technical details.

Detection Methods for CVE-2026-42861

Indicators of Compromise

Variable resources whose workspaceId changed without a corresponding administrative action
Unexpected updatedDate or createdDate values on variable records that do not match expected workflow events
API requests to the variable update endpoint that include fields outside the documented mutable set

Detection Strategies

Review Flowise application logs for PUT or PATCH requests against variable endpoints containing workspaceId in the payload
Compare workspace ownership of variables against expected tenant assignments to identify drift
Alert on authenticated users issuing variable update requests that target workspaces they do not normally interact with

Monitoring Recommendations

Enable verbose audit logging for all CRUD operations on variable, credential, and workspace resources
Forward Flowise API and reverse proxy logs to a centralized analytics platform for cross-tenant correlation
Establish baselines of normal per-user workspace activity and flag deviations

How to Mitigate CVE-2026-42861

Immediate Actions Required

Upgrade FlowiseAI Flowise to version 3.1.2 or later as published in the Flowise 3.1.2 Release Notes
Audit variable records across all workspaces to confirm workspaceId assignments match expected tenant boundaries
Rotate any secrets or credentials stored as Flowise variables if cross-workspace tampering is suspected

Patch Information

The issue is fixed in Flowise version 3.1.2. The patch is referenced in the GitHub Security Advisory GHSA-6fw7-3q8r-m5vj. Administrators running self-hosted Flowise deployments should plan an upgrade window and verify integrity of variable data post-upgrade.

Workarounds

Restrict network access to the Flowise API so only trusted operators can authenticate until the patch is applied
Reduce the number of users with variable update permissions in multi-workspace deployments
Place Flowise behind a reverse proxy that strips unexpected fields such as workspaceId from variable update request bodies

bash

# Upgrade self-hosted Flowise to the patched version
npm install -g flowise@3.1.2
# Or with Docker
docker pull flowiseai/flowise:3.1.2
docker stop flowise && docker rm flowise
docker run -d --name flowise -p 3000:3000 flowiseai/flowise:3.1.2