CVE-2026-61736: LightRAG Critical CORS Credential Bypass (CVSS 9.3)

Overview

A critical vulnerability has been identified in LightRAG, the popular open-source retrieval-augmented generation (RAG) framework, which ships with a dangerously permissive CORS configuration by default. The issue, tracked as CVE-2026-61736 with a CVSS score of 9.3 (Critical), allows any origin to make credentialed cross-origin requests to the LightRAG API server.

The root cause lies in lightrag/api/lightrag_server.py, where the server defaults to:

CORS_ORIGINS="*"
allow_credentials=True

According to the CORS specification, combining a wildcard origin (*) with allow_credentials=True via Starlette's CORSMiddleware effectively whitelists every origin for credentialed requests — meaning cookies, authorization headers, and TLS client certificates are forwarded from any attacker-controlled site.

Impact

An attacker who can lure an authenticated LightRAG user to a malicious webpage can:

• Read or exfiltrate the victim's knowledge graph data via cross-origin fetch requests
• Insert or delete graph nodes and relationships
• Query the LLM backend using the victim's API credentials
• Fully compromise multi-tenant deployments where users share a single LightRAG instance

The severity is amplified by LightRAG's common deployment pattern: many organizations run it as an internal tool behind an SSO proxy or basic auth layer, assuming cross-origin protections are enforced at the browser level. This vulnerability bypasses that assumption entirely.

Affected Versions

Remediation

Update Immediately

Upgrade LightRAG to version 1.5.4 or later:

pip install --upgrade lightrag-hku

Manual Mitigation (if unable to upgrade)

Explicitly configure CORS with an allowlist of trusted origins:

from lightrag.api.lightrag_server import create_app
 
app = create_app(
    cors_origins=["https://your-trusted-domain.com"],
    allow_credentials=True
)

Never use CORS_ORIGINS="*" alongside allow_credentials=True in production.

Network-Level Controls

If running LightRAG behind a reverse proxy (nginx, Traefik, Caddy), ensure CORS headers set by the proxy override or remove the application's permissive defaults:

add_header 'Access-Control-Allow-Origin' 'https://your-domain.com' always;
add_header 'Access-Control-Allow-Credentials' 'true' always;

Detection

Check your LightRAG startup logs or configuration for the default CORS_ORIGINS=* setting:

grep -r "CORS_ORIGINS" /path/to/lightrag/
grep -r "allow_credentials" /path/to/lightrag/

Review your web server access logs for cross-origin preflight (OPTIONS) requests from unexpected origins:

grep 'OPTIONS' /var/log/nginx/access.log | grep 'Origin:'

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

References

• NVD Entry: CVE-2026-61736
• LightRAG GitHub Repository
• OWASP: CORS Misconfiguration
• MDN Web Docs: CORS with Credentials