# CVE-2026-86543: knowns before 0.30.0 Unauthenticated Management API Exposure

> Attackers can access the unauthenticated management API to provision public tunnels, exposing internal services to the internet.

- **Severity:** Critical 9.3 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 7 Sep 2026
- **Updated:** 24 Sep 2026
- **Also known as:** GHSA-fc85-99vc-9c75, GHSA-pcf3-jgx6-7m94

## What is CVE-2026-86543?

CVE-2026-86543 is a critical missing authorization vulnerability in knowns-dev knowns, published on 7 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-306 (Missing Authentication for Critical Functionality)

## Which versions are affected by CVE-2026-86543?


## How do I fix CVE-2026-86543?

No fix has been published for CVE-2026-86543 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-86543 being exploited?

There is no known exploitation of CVE-2026-86543 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-86543 and fix it if it is affected.

What it is: CVE-2026-86543 is a critical missing authorization vulnerability in knowns-dev knowns, published on 7 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-86543 in the wild and no public exploit code.

Affected product: knowns-dev knowns. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-86543/ (Markdown: https://insights.sbomify.com/CVE-2026-86543/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-86543
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-86543
- OSV: https://osv.dev/vulnerability/CVE-2026-86543

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-86543/
Summaries are generated and may contain mistakes; the official description above is the record.