9router has an Incomplete Fix: Local-Only Access Gate Bypass in 9router via Host Header SpoofING

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:N

EPSS

• CVE-2026-49353: 0.34% estimated exploitation activity in the next 30 days; percentile 26.94 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The fix for CVE-2026-46339 (unauthenticated RCE via unprotected MCP plugin routes) introduced a local-only access gate in src/dashboardGuard.js that restricts spawn-capable routes (/api/mcp/, /api/tunnel/, /api/cli-tools/) to loopback requests. The gate determines "local" by inspecting the Host and Origin HTTP headers rather than the TCP source address. When 9router is deployed behind a reverse proxy, tunnel (Cloudflare Tunnel, Tailscale — both natively supported), or is subject to DNS rebinding, these headers are attacker-controlled, allowing the local-only gate to be bypassed. A second factor (CLI token or JWT cookie) is required by canAccessLocalOnlyRoute(), but the CLI token is a deterministic HMAC of the machine ID (getConsistentMachineId), which is stable and predictable on cloud VMs. If the attacker can obtain or guess the machine ID (e.g., via another information disclosure, or on shared-tenant infrastructure), the full chain to MCP child process stdin injection is…

Published by the source

2 Jul 2026, 21:13 UTC

Last modified by the source

6 Jul 2026, 10:44 UTC

Source last checked

26 Oct 2026, 12:56 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-6g2f-w7g3-77vf

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-6g2f-w7g3-77vf

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# Patch Next advisory brief: CVE-2026-49353

Advisory: 9router has an Incomplete Fix: Local-Only Access Gate Bypass in 9router via Host Header SpoofING
IDs: CVE-2026-49353, GHSA-6g2f-w7g3-77vf
Record: https://patchnext.com/advisories/cve-2026-49353 (revision 2, source checked 26 Oct 2026, 12:56 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm 9router: affected <= 0.4.55

## Suggested inspection (read-only)
- `npm ls 9router --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on 9router.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-6g2f-w7g3-77vf (OSV record GHSA-6g2f-w7g3-77vf lists affected ranges: npm 9router >=0 <=0.4.55)
- Verified: https://github.com/advisories/GHSA-6g2f-w7g3-77vf (GitHub-reviewed advisory GHSA-6g2f-w7g3-77vf lists affected ranges: npm 9router >=0 <=0.4.55)

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