MSRXCVE-2026-56681
CVE-2026-56681
9Router: Authentication Bypass in Public LLM API via Spoofable X-9r-Real-Ip Header
CVSS 3.1 · CNA
chance of exploitation in the next 30 days (EPSS; higher than 65% of CVEs)
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.
Scores
Affected packages and fixed versions
| Package | Ecosystem | Fixed in |
|---|---|---|
| 9router | npm | 0.5.8 |
Affected products
- decolua 9router: < 0.5.6
Weakness: CWE-807
Also known as: GHSA-5mj8-gf6m-fhw8
3 references (advisories, patches, write-ups)
- 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
Sources: CVE.org, OSV.dev, FIRST EPSS. Missing ones did not answer or have no record yet.