Auth bypass in Knowns-Dev Knowns
CVE-2026-86543
knowns versions before 0.30.0 serve the management API without authentication on all network interfaces by default, with no password required on fresh installations. Attackers can access the unauthenticated /api/tunnel/start endpoint to provision a public tunnel and republish the API at a publicly accessible address.
Vulnerability class: Broken Authentication
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.009 (58.0th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 58th percentile — 58.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.009 · change: +0.004
Affected products
Weakness classification (CWE)
References
- Browser listener binds 0.0.0.0 (v0.29.1) (technical-description)
- AuthManager.Middleware is a no-op when no password is configured (v0.29.1) (technical-description)
- POST /api/tunnel/start has no authorization check of its own (v0.29.1) (technical-description)
- knowns fix commit 878a02cb7cc1 (patch)
- knowns v0.30.0 Release Notes (release-notes)
- GitHub Security Advisory (GHSA-fc85-99vc-9c75) (vendor-advisory)
- VulnCheck Advisory: knowns before 0.30.0 Unauthenticated Management API Exposure (third-party-advisory)
Frequently asked questions
- What is CVE-2026-86543?
- CVE-2026-86543 is a critical-severity vulnerability in Knowns-Dev Knowns, classified under Missing Authentication for Critical Function. CVSS score: 9.8/10. Published 2026-09-07.
- How severe is CVE-2026-86543?
- Critical severity. CVSS v3 base score is 9.8 out of 10.