| Package | Affected versions | Patched versions |
|---|---|---|
| github.com/obot-platform/obot | < 0.21.1 | 0.21.1 |
If you have the MCP Server ID, you can connect to the MCP server even if you don't have permissions to the server.
The MCP gateway endpoint /mcp-connect/{mcp_id} does not enforce Access Control Rules (ACRs). Any authenticated Obot user who possesses an MCP Server ID can connect to that server through the gateway — including making tool calls — regardless of whether they are a member of any MCP Registry that grants access to the server.
In practice this means any User can fully use MCP servers that the administrator believed were restricted to specific groups.
Reporter estimate: Critical.
| CVSS 3.1 metric | Value |
|---|---|
| Attack Vector | Network |
| Attack Complexity | Low |
| Privileges Required | Low (authenticated Obot user, any role ≥ Basic) |
| User Interaction | None |
| Scope | Changed (Obot authorization bypass enables access to data and operations on an upstream third-party service via Obot's stored OAuth credentials) |
| Confidentiality | High |
| Integrity | High (many MCP servers expose write tools — e.g. updateEmployee, submitTimeoffRequest, ticket creation, file writes) |
| Availability | None |
| Vector | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N |
| Score | 9.3 / Critical |
The upstream impact depends on which MCP servers are deployed and what scope their stored credentials hold; the bound is "everything the platform's stored OAuth/API credentials can reach."
Confirmed on obot v0.21.0.
The intended flow is that a user's authorization is checked during the OAuth process with Obot.
/mcp-connect URL in this case). Obot correctly determines the user's authorization during this flow.Running one of these products? Scan your site to see whether it exposes a vulnerable version.
Scan my site freeTested on obot v0.21.0.
Setup:
everyone group from the relevant rule.Exploit:
Sign in as the Basic User.
Verify the UI does not list the server in any connector picker (it does not — that path is correctly gated).
Manually craft and call the gateway URL:
POST https://<obot>/mcp-connect/<mcp_server_id>
Authorization: <session cookie or API key>
Content-Type: application/json
{"jsonrpc":"2.0","id":1,"method":"tools/list"}
Observe a successful response listing the server's tools.
Issue an actual tool call:
{"jsonrpc":"2.0","id":2,"method":"tools/call",
"params":{"name":"<sensitive_tool>","arguments":{...}}}
The exploit works equally well via Claude Desktop / Claude Code / any MCP-aware client by configuring the gateway URL as a remote MCP endpoint with the user's API key.