9router: Unauthenticated `/v1` proxy access via `Host`-header spoofing → open AI relay + SSRF — GHSA-86M2-FCXQ-5Q7C

Summary

## Summary 9router's request guard decides a request is "local" (and therefore exempt from API-key auth on the `/v1` LLM proxy) by reading the **client-controlled `Host` header**. Because 9router binds `0.0.0.0` by default (and the CLI misleadingly prints "localhost"), a remote, unauthenticated attacker who can reach the port can send `Host: localhost` to be treated as local and obtain `/v1` proxy access with **no…

Timeline

Published by source

2026-08-28

Risk context

• Reported severity or threat level: high.
• Reported CVSS score: 8.2 out of 10.
• Reported EPSS value: 0.00323.
• Review exposure for the affected product or family: npm: 9router.

Product

npm: 9router

What to do

General, cautious steps (verify details in the official source):

• Prioritize patching or mitigation immediately (treat as actively risky).
• Identify affected product versions in your inventory and verify whether you are impacted.
• Apply vendor patches/updates or recommended mitigations as soon as available.
• Read the official advisory for exact affected versions and remediation steps.

Official advisory

• Read the official source
• CVE Record
• NVD

Evidence and provenance

Canonical advisory ID

GHSA-86M2-FCXQ-5Q7C

Source

GitHub

Vendor

GitHub

Published by source

2026-08-28

Last source activity

2026-08-28

Additional identifiers

CVE-2026-55641

Curated by

hlukh.ch

Related advisories and connections

These advisories are connected by shared CVE, product, vendor, source, or time signals.