---
title: "HOST-CTR-001 Docker API Exposed Over TCP Without TLS"
canonical: https://openvapt.com/checks/HOST-CTR-001.html
html: https://openvapt.com/checks/HOST-CTR-001.html
site: OpenVAPT, https://openvapt.com/
license: OpenVAPT Source-Available Licence 1.3, https://openvapt.com/legal/licence-text.html
modified: 2026-10-14
version: 0.1.0-alpha.6
---

# HOST-CTR-001 Docker API Exposed Over TCP Without TLS

Checks whether the Docker daemon is configured to listen on a TCP socket without TLS client verification.

- Domain: Server
- Severity: Critical
- Control category: Network Exposure
- Fix effort: low
- CVSS v3.1 vector: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H`
- CIS Controls v8: 4.8
- NIST CSF 2.0: PR.PS-01, PR.IR-01
- CWE: CWE-306, CWE-319
- OWASP Top 10 2021: A05:2021, A07:2021
- NIST SP 800-53 Rev. 5: AC-3, SC-8

## Why It Matters

The Docker API is equivalent to root on the host. Exposed over TCP without mutual TLS, anyone who can reach the port can start a privileged container and take over the machine; this is a common cause of cryptomining infections.

## How It Detects

Reads /etc/docker/daemon.json (hosts and tlsverify) and Docker systemd unit files and drop-ins for -H tcp:// flags.

## How to Fix

Remove tcp:// listeners and use the local Unix socket or SSH (docker context with ssh://). If remote access is unavoidable, enable tlsverify with client certificates and restrict the port in the firewall.

## How to Verify

```
ss -tlnp | grep -E ':(2375|2376)'  and  grep -r 'tcp://' /etc/docker /etc/systemd/system/docker.service.d
```

## Learn the Theory

- [P9 Containers and Kubernetes](https://openvapt.com/academy/p9.md)

## References

- [Docker documentation, Protect the Docker daemon socket](https://docs.docker.com/engine/security/protect-access/)
- [OWASP Docker Security Cheat Sheet](https://cheatsheetseries.owasp.org/cheatsheets/Docker_Security_Cheat_Sheet.html)

## Source Code

https://github.com/OpenVAPT/openvapt/blob/574f7f3333c44b75a3c649e2d93a76d507f75adf/internal/checks/host/containers.go

Run it: `openvapt scan --only HOST-CTR-001`. Read it offline: `openvapt explain HOST-CTR-001`.

---

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