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EUVD-2026-369621

fkie_cve-2026-55837

dbt-mcp is a Model Context Protocol server for interacting with dbt. Prior to 1.20.0, the local OAuth helper in src/dbt_mcp/oauth/fastapi_app.py exposes GET /dbt_platform_context without authentication or Host validation after a user completes the dbt Platform OAuth flow. The endpoint returns the full DbtPlatformContext, including access_token and refresh_token values persisted by the context manager, to any process that can reach 127.0.0.1:6785. The absence of TrustedHostMiddleware allows a remote attacker to use DNS rebinding against a victim's browser because the helper accepts arbitrary Host headers, while a co-located process can request the endpoint directly. The stolen tokens provide immediate dbt Platform API access as the victim and persistent access through the refresh token, allowing access to or modification of projects, jobs, environment secrets, and related account data. This issue is fixed in version 1.20.0.

GHSA-jr33-mw75-7j8f — dbt MCP Server: Unauthenticated OAuth Context Endpoint Leaks dbt Platform Tokens

Affected: PyPI: dbt-mcp

## Unauthenticated OAuth Context Endpoint Leaks dbt Platform Tokens

### Summary

The local OAuth helper FastAPI server bundled with `dbt-mcp` exposes the `GET /dbt_platform_context` endpoint without any form of authentication or host-origin validation. After a user completes the OAuth login flow against dbt Cloud (cloud.getdbt.com), the endpoint returns the full `DbtPlatformContext` object — including the victim's `access_token` and `refresh_token` for the dbt Platform API — verbatim to any caller that can reach `127.0.0.1:6785`. An attacker who can direct the victim's browser to the helper origin via DNS rebinding, or who has co-located process access on the same host, can silently exfiltrate both tokens. The stolen bearer token grants full dbt Cloud API access as the victim; the refresh token enables persistent access beyond the original token's expiry. **CVSS Base Score: 8.0 (High).**

### Details

During the OAuth login flow, `dbt-mcp` launches an embedded FastAPI server (the "OAuth helper") bound to `127.0.0.1` starting on port `6785` (configured at `src/dbt_mcp/config/credentials.py:34`, `OAUTH_REDIRECT_STARTING_PORT = 6785`). After the OAuth callback is handled, the helper persists the full token context to disk and continues serving requests.

**Data flow from source to sink:**