9Router prior to v0.5.2 enforces an API‑key guard on endpoints such as /v1 and /api/v1, but the path /codex is omitted from this check. Because next.config.mjs rewrites requests to /codex/* into /api/v1/responses, an unauthenticated attacker can target the /codex endpoint and bypass the guard entirely. The server then forwards the request to the upstream LLM provider using LM calls without authorization. The issue is fixed in release v0.5.2 and no other vendors or products are listed as affected.

The affected product is 9router from decolua. All releases prior to version 0.5.2 are vulnerable. No other vendors or products are listed as affected.

The CVSS score of 8.6 indicates a high severity for this flaw. The EPSS score is less than 1%, suggesting exploitation is unlikely but still possible. The vulnerability is not listed in the CISA KEV catalog. The likely attack vector is remote network access via HTTP; an unauthenticated user only needs to craft a request to /codex/* to trigger the attack.