HIGH 8.6 GitHub
CVE-2026-55638
9router: Unauthenticated LLM proxy access via /codex rewrite authorization bypass
## Summary
9router exposes an OpenAI/Anthropic-compatible LLM proxy. Remote access to this proxy is intended to be protected by an API-key check in the Next.js middleware.
However, 9router also defines a rewrite that maps `/codex/*` to the backend LLM endpoint `/api/v1/responses`. The middleware authorization decision is made on the incoming request path before the rewrite is applied. Because `/codex` is not included in the middleware's protected LLM API prefix list, requests to `/codex/*` byp
Affected Products
- npm/9router < 0.5.2
References
- https://github.com/advisories/GHSA-8gmq-j984-vp4r
- https://github.com/decolua/9router/security/advisories/GHSA-8gmq-j984-vp4r
- https://nvd.nist.gov/vuln/detail/CVE-2026-55638
- https://github.com/decolua/9router/commit/b282f0554972ea35281520738759d76abcd0b0b3
This high severity vulnerability with a CVSS score of 8.6 was published on 2026-08-28 via GitHub. Affected: npm/9router < 0.5.2.
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