Vulnerability · Published Sep 22, 2026 · Assigned by GitHub_M

CVE-2026-566819Router: Authentication Bypass in Public LLM API via Spoofable X-9r-Real-Ip Header

High 7.3

In plain English

A high-severity security flaw in 9router from decolua. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 1.1% (higher than 66% of all known vulnerabilities). Ready-made attack tooling exists: Nuclei. Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.3High

Exploit odds (30 days)1.1%top 33.8% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack tooling1Nuclei

Official description

9Router is an AI router & token saver. Prior to 0.5.6, 9Router deployments that allow requests to reach Next.js without the sanitizing custom-server.js wrapper trust the client-supplied X-9r-Real-Ip header in src/dashboardGuard.js when isLocalRequest decides whether canAccessPublicLlmApi may skip API-key validation for /api/v1/* routes. A remote unauthenticated attacker can set X-9r-Real-Ip to 127.0.0.1 and be classified as a local client, including on the verified GET /api/v1/models route. This permits unauthorized use of the instance owner's configured LLM providers, consumption of paid credits, and enumeration of configured providers and models. This issue is fixed in version 0.5.6.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
npm	9router	0.5.8	GHSA-5mj8-gf6m-fhw8

Affected products (as reported)

Vendor	Product	Versions
decolua	9router	< 0.5.6

Weakness: CWE-807 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

References

https://github.com/decolua/9router/security/advisories/GHSA-5mj8-gf6m-fhw8 x_refsource_CONFIRM
https://github.com/decolua/9router/commit/efd20be8d81ef2e256a7037f3aa78e6b567b5fd3 x_refsource_MISC
https://github.com/decolua/9router/releases/tag/v0.5.6 x_refsource_MISC