7.6

CVSS Score

4.0

-

CVSS Score

Basic Information

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CVE-2026-42861

CVE-2026-42861: Flowise: Mass Assignment in Variable Update Endpoint Allows Cross-Workspace Resource Reassignment

Flowise is a drag & drop user interface to build a customized large language model flow. Prior to version 3.1.2, a mass assignment vulnerability exists in the variable update endpoint of FlowiseAI. The endpoint allows authenticated users to modify server-controlled properties such as workspaceId, createdDate, and updatedDate when updating a variable resource. Due to missing server-side validation and authorization checks, an attacker can manipulate the workspaceId field and reassign variables to arbitrary workspaces. This behavior may break tenant isolation in multi-workspace environments. This issue has been patched in version 3.1.2.

(GitHub Advisory)

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CVE-2026-42861

CVE-2026-42861:

7.6

CVSS Score

4.0

-

CVSS Score

Basic Information

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Technical Details

SSVC / BOD 26-04 ↗

Exploitation pocAutomatable NoTech Impact Partial

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Package Name	Ecosystem	Vulnerable Versions	First Patched Version
flowise	npm	<= 3.1.1	3.1.2

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The vulnerability is a mass assignment issue in FlowiseAI's variable management endpoints. The root cause is the use of Object.assign() in the createVariable and updateVariable controller functions (packages/server/src/controllers/variables/index.ts), which directly mapped user-provided JSON objects to database entities without proper input sanitization. This allowed authenticated users to overwrite protected, server-controlled properties like workspaceId, createdDate, and updatedDate.

Exploitation of this vulnerability allows an attacker to reassign a variable to any workspace by manipulating the workspaceId field in a PUT request to /api/v1/variables/{variableId}. This breaks tenant isolation in multi-workspace deployments.

The patch addresses this vulnerability at two levels:

Controller Layer: The Object.assign() calls in createVariable and updateVariable were replaced with an explicit allowlist, ensuring only permitted fields (name, value, type) can be modified by the user.
Service Layer: As a defense-in-depth measure, the updateVariable function in packages/server/src/services/variables/index.ts was modified to explicitly preserve the original workspaceId of a variable during an update, preventing any change to this field at the database level.

During exploitation, a runtime profiler would show calls to the updateVariable function in the controller, which in turn calls the updateVariable function in the service. Therefore, all identified functions are critical runtime indicators for this vulnerability.

Vulnerable functions

updateVariable

packages/server/src/controllers/variables/index.ts

This function handles the `PUT /api/v1/variables/{variableId}` endpoint. The vulnerability is in the line `Object.assign(updatedVariable, body)`, which performs mass assignment of all properties from the user-controlled request body to the `updatedVariable` object. This allowed an attacker to overwrite protected, server-controlled properties such as `workspaceId`, leading to cross-workspace resource reassignment.

createVariable

packages/server/src/controllers/variables/index.ts

Similar to the `updateVariable` function, this function was vulnerable to mass assignment. The use of `Object.assign(newVariable, body)` allowed an attacker to set protected properties like `workspaceId` when creating a new variable, potentially creating resources in a workspace they don't have access to.

updateVariable

packages/server/src/services/variables/index.ts

This service-layer function was modified as a defense-in-depth measure. While the primary vulnerability was in the controller, this function's change ensures that the `workspaceId` of a variable cannot be changed during an update. It explicitly saves the original `workspaceId` before merging changes and restores it, preventing the reassignment at the database level. This function would appear in a stack trace during exploitation.

Vulnerability Intelligence
Miggo AI

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WAF Rule

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Reasoning

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