CVE-2026-55638 9router: Unauthenticated LLM proxy access via /codex rewrite authorization bypass
Unauthenticated attackers can bypass API key checks on the /codex endpoint to use stored LLM provider credentials for unauthorized upstream calls.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-55638?
CVE-2026-55638 is a high-severity authentication bypass vulnerability in decolua 9router, published on 10 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
9Router is an AI router & token saver. Prior to 0.5.2, 9router protects /v1, /v1beta, /api/v1, and /api/v1beta in src/dashboardGuard.js but omits /codex before next.config.mjs rewrites /codex/* to /api/v1/responses. A remote unauthenticated attacker can send requests to /codex/* to bypass the API-key gate and cause the server to make upstream provider calls using operator-stored LLM provider credentials. This issue is fixed in version 0.5.2.
Which versions are affected by CVE-2026-55638?
2 open source packages ship an affected version, including 9router.
| Package | Affected | Fixed in |
|---|---|---|
9router npm | All versions | 0.5.2 |
9router npm | All versions | 0.5.2 |
How do I fix CVE-2026-55638?
Upgrade 9router to 0.5.2 or later.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-55638 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55638 exists.
Sources
Also known as GHSA-8gmq-j984-vp4r.