GHSA-p4fx-23fq-jfg6

Описание

Summary

The tool update endpoint (POST /api/v1/tools/id/{id}/update) is missing the workspace.tools permission check that is present on the tool create endpoint. This allows a user who has been explicitly denied tool management capabilities ( and who the administrator considers untrusted for code execution ) to replace a tool's server-side Python content and trigger execution, bypassing the intended workspace.tools security boundary.

Open WebUI's security policy correctly states that workspace.tools is the trust boundary for code execution: "Granting a user the ability to create Tools is equivalent to giving them shell access to the server." This vulnerability breaks that boundary. A write access grant on a single tool is sufficient to bypass workspace.tools entirely.

This is not a report about exec() being unsandboxed (that is acknowledged as intended behavior). This is a report about a missing authorization check that allows an untrusted user to reach the exec() sink that should be gated behind workspace.tools.

Root Cause

The create and update endpoints for tools have asymmetric authorization checks. The create endpoint enforces the workspace.tools permission; the update endpoint does not.

Create endpoint, enforces workspace.tools

File: backend/open_webui/routers/tools.py, lines 326-345

Update endpoint does NOT enforce workspace.tools

File: backend/open_webui/routers/tools.py, lines 451-485

The write access grant is a collaboration primitive used across the application (knowledge bases, prompts, models, tools) for content editing. On every other resource type, a write grant allows editing metadata and content. On tools specifically, because the update endpoint triggers exec(), a write grant silently escalates to code execution but only because the workspace.tools check is missing. If the check were present (as it is on create), the write grant would not confer execution privilege.

Prerequisites

1. Attacker (Bob): A regular user account with no workspace.tools permission. workspace.tools is disabled by default (config.py:1364-1366), so this is the default state for all non-admin users.
2. Collaborator (Alice): A user with workspace.tools permission who creates a tool and grants write access to Bob. This is a normal collaboration workflow Alice is sharing editing access, not granting code execution rights.
3. No admin action required beyond the initial workspace.tools grant to Alice (which is the intended, documented workflow).

Note on default configuration: The workspace.tools permission defaults to false. An administrator must explicitly enable it for at least one user (Alice). This is a documented, recommended workflow the security policy explicitly describes granting workspace.tools to trusted users. The vulnerability is not that Alice has this permission; it is that Bob can bypass it.

Proof of Concept

Environment

Default configuration. Admin creates an account, enables workspace.tools for trusted users via Admin Panel > Settings > User Permissions.

Step-by-step reproduction

Step 1 Setup users

Create two non-admin users: Alice (trusted, will get workspace.tools) and Bob (untrusted, will NOT get workspace.tools).

Step 2 Admin enables workspace.tools globally

This is the documented workflow for allowing trusted users to build tools.

Step 3 Alice creates a benign tool

Step 4 Alice grants write access to Bob (collaboration)

Alice wants Bob to be able to edit the tool's description or parameters. This is a standard collaboration feature.

Step 5 Admin disables workspace.tools

Admin revokes the global permission. Now neither Alice nor Bob (nor any non-admin) should be able to execute code via tools.

Step 6 Verify Bob CANNOT create tools

Step 7 Bob updates the tool content → code execution (the bypass)

Bob replaces the tool's Python content. The update endpoint does not check workspace.tools, only the write access grant. The new content is passed to exec().

Actual PoC Output

The following is a complete run of the automated PoC script:

Burp Collaborator Evidence

The container made an outbound HTTP POST to a Collaborator server, confirming code execution from within the container:

Security Boundary Violated

Open WebUI's security policy defines workspace.tools as the trust boundary for code execution:

"Tool creation is controlled by the workspace.tools permission, which is disabled by default for non-admin users and should only be granted to fully trusted users who are equivalent to system administrators in terms of trust. Granting a user the ability to create Tools is equivalent to giving them shell access to the server."

This vulnerability breaks that boundary:

The update endpoint substitutes AccessGrants.has_access('write') where has_permission('workspace.tools') should be. A write grant is a collaboration primitive for editing content; workspace.tools is the code execution trust boundary. These are different privilege levels, but the update endpoint conflates them.

Impact

An attacker with a regular user account and a write access grant on any single tool can:

• Execute arbitrary server-side code as root (PID 1 in the default Docker deployment)
• Read sensitive environment variables (WEBUI_SECRET_KEY, OPENAI_API_KEY, etc.)
• Read/write the application database (all users' chats, files, API keys)
• Read arbitrary files from the container filesystem
• Make outbound network requests to internal services

The attacker never needs workspace.tools permission. The administrator's explicit decision to deny this user code execution capability is bypassed.

Remediation

Recommended Fix

Add the workspace.tools permission check to the update endpoint, matching the create endpoint's authorization gate:

File: backend/open_webui/routers/tools.py, after line 481 (after the existing access check)

This allows users with write grants to update tool metadata (name, description, valves) without workspace.tools, but requires the permission for content changes that trigger code execution.