Reliance on Untrusted Inputs in a Security Decision Affecting 9router package, versions <0.5.8
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-JS-9ROUTER-21694030
- published24 Oct 2026
- disclosed22 Sept 2026
- creditUnknown
Introduced: 22 Sep 2026
CVE-2026-56681 (opens in a new tab)How to fix?
Upgrade 9router to version 0.5.8 or higher.
Overview
9router is a 9Router CLI - Start and manage 9Router server
Affected versions of this package are vulnerable to Reliance on Untrusted Inputs in a Security Decision via the IP address resolution logic in custom-server.js, where forwarding headers such as X-Forwarded-For and X-Real-IP are trusted regardless of whether the TCP peer is a local reverse proxy. An attacker making a direct connection to the server can supply arbitrary values in these headers, causing the server to record and act on a spoofed client IP address instead of the true peer address. This allows the attacker to bypass IP-based access controls or rate limiting, potentially enabling consumption of paid API credits or unauthorized access to the instance.