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Vulnerability record · CVE-2026-86543 · published 7 September 2026

CVE-2026-86543: Missing authentication for critical function vulnerability

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.

9.3 CVSS 4.0 Critical EPSS 0.86% · top 43.3% CWE-306 · Missing authentication for critical function Deferred
9.3CVSS 4.0 base score
0.86%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
7References
14 Sep 2026Last modified by NVD

Description

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.

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

References

LinkTags
https://github.com/knowns-dev/knowns/blob/v0.29.1/internal/cli/browser.go#L193-L200
https://github.com/knowns-dev/knowns/blob/v0.29.1/internal/server/auth.go#L80-L86
https://github.com/knowns-dev/knowns/blob/v0.29.1/internal/server/routes/tunnel.go#L26-L38
https://github.com/knowns-dev/knowns/commit/878a02cb7cc14f0a592fdfda7a520af3cac500fb
https://github.com/knowns-dev/knowns/releases/tag/v0.30.0
https://github.com/knowns-dev/knowns/security/advisories/GHSA-fc85-99vc-9c75
https://www.vulncheck.com/advisories/knowns-before-0.30.0-unauthenticated-management-api-exposure

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Source: NIST National Vulnerability Database (record CVE-2026-86543), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.