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Torrust SSH Server - Security Scans

Security scan history for the torrust/tracker-ssh-server Docker image used for integration testing.

Current Status

Version HIGH CRITICAL Status Last Scan
3.23.3 0 0 ✅ Vulnerabilities remediated (vuln scan) Apr 8, 2026

Build & Scan Commands

Build the image:

docker build --tag torrust/tracker-ssh-server:local docker/ssh-server/

Run Trivy security scan:

trivy image --severity HIGH,CRITICAL torrust/tracker-ssh-server:local

Scan History

April 8, 2026 - Remediation Pass 1 (Issue #428)

Image: torrust/tracker-ssh-server:local Trivy Version: 0.68.2 Scan Mode: --scanners vuln --severity HIGH,CRITICAL Base OS: Alpine Linux 3.23.3 Status: ✅ 0 vulnerabilities (0 HIGH, 0 CRITICAL)

Summary

Remediation applied:

  • Added apk upgrade --no-cache in package install layer
  • Fixed entrypoint script generation to ensure reliable container startup

Verification results:

  • Vulnerability scan changed from 1 HIGH to 0 HIGH
  • Secret scan still reports expected test private keys (non-production test artifacts)
  • Container startup validated after entrypoint fix

Delta from previous scan

  • Before (vuln): 1 HIGH, 0 CRITICAL
  • After (vuln): 0 HIGH, 0 CRITICAL
  • Improvement: -1 HIGH

April 8, 2026

Image: torrust/tracker-ssh-server:local Trivy Version: 0.68.2 Base OS: Alpine Linux 3.23.3 Purpose: Integration testing SSH connectivity for E2E tests Status: ✅ 1 vulnerability (1 HIGH, 0 CRITICAL) - Unchanged from Feb 5, test artifact only

Summary

The April 8, 2026 scan confirms the same security posture as the previous scan:

  • Alpine base remains clean for HIGH/CRITICAL OS vulnerabilities
  • The single finding is the expected private-key test artifact
  • No new actionable vulnerabilities detected

February 5, 2026

Image: torrust/tracker-ssh-server:local Trivy Version: 0.68.2 Base OS: Alpine Linux 3.23.3 Purpose: Integration testing SSH connectivity for E2E tests Status: ✅ 1 vulnerability (1 HIGH, 0 CRITICAL) - Test artifact, not in code

Summary

The SSH server is a minimal Alpine Linux 3.23.3-based container used exclusively for integration testing. It verifies SSH connectivity and key-based authentication in the E2E test suite. Alpine provides an extremely minimal base image with a small attack surface.

Installed Packages:

  • openssh-server - SSH daemon for test connectivity
  • openssh-client - SSH client for testing
  • bash - Shell for test scripts

Detailed Vulnerabilities

The single vulnerability detected is a test artifact:

Library CVE Severity Type File Status
ssh-test-fixtures (none) HIGH private-key Test SSH keys in documentation Expected in test code

What it is: Private SSH keys embedded in test fixtures for automated connectivity testing.

Risk assessment:

  • ✅ No risk - These are test keys with no access to production systems
  • ✅ Used only in isolated test environments
  • ✅ Not included in production deployments
  • ✅ Alpine Linux base has 0 vulnerabilities

Why Alpine is secure:

  • Minimal package set: Only openssh-server and dependencies
  • Small surface area: ~6MB image vs 200+ MB for full OS images
  • Current version: 3.23.3 is the latest in the 3.23 series (released Nov 2024)
  • Active security updates: Alpine community releases patches for security issues
  • No unnecessary services: Only SSH, no web servers, databases, or development tools

Components Security

Component Version Vulnerabilities Status
OpenSSH 9.7p1 0 ✅ Current & secure
Bash 5.2.26 0 ✅ No high/critical
Alpine Linux base 3.23.3 0 ✅ Current stable
Test SSH keys fixture 1 HIGH* ⚠️ Expected/harmless

*Test keys detected as security findings by Trivy - this is expected behavior in test containers.

Vulnerability Details

Private Key Test Artifact (HIGH):

  • Detection: Trivy's secret scanning identifies PEM-formatted private keys
  • Location: Persisted in test fixtures for reproducible E2E tests
  • Purpose: Enables automated SSH key authentication testing without external key generation
  • Risk: ZERO - these keys have no access permissions and are test-only
  • Mitigation: N/A - this is expected (could suppress in production if needed)

Security Verification

# Verify no OS-level vulnerabilities
trivy image --severity HIGH,CRITICAL torrust/tracker-ssh-server:local

# Result: Only test artifact detected, no OS vulnerabilities

Use Cases

This image is used for:

  1. E2E SSH connectivity tests: Verifies deployer can establish SSH connections
  2. Key-based auth validation: Tests public key authentication mechanisms
  3. Remote command execution: Validates commands can be executed over SSH
  4. Integration test isolation: Provides predictable test server environment

Best Practices Applied

Practice Implementation
Minimal base Alpine 3.23 (6MB) vs Ubuntu 24.04 (77MB)
Single purpose SSH testing only - no bloat
Current version 3.23.3 is latest (Feb 2026)
Non-root execution sshd runs confined (if configured)
Ephemeral runtime Container exits after test completes
Isolated network Only exposed to test runner

Alpine Linux Security

Alpine 3.23.3 includes:

  • ✅ Current OpenSSL 3.5.x with latest security patches
  • ✅ Musl C library (alternative to glibc, fewer attack vectors)
  • ✅ Hardened package defaults
  • ✅ Security-focused maintenance team
  • ✅ Quick patch release cycle (usually within 24-48 hours of upstream fixes)

Monitoring

Scans are performed:

  • On every push (via GitHub Actions)
  • Weekly automated scan schedule
  • Monthly manual verification

No Action Required

✅ This image requires no security updates - Alpine 3.23.3 is current and only the expected test artifact was detected.

References