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Insecure service configuration - Host verification

Description​

The system does not properly restrict incoming conections from unknown external hosts.

Impact​

Establish conections with untrusted machines.

Recommendation​

Validate that incoming conections come from trusted hosts already defined in the known_hosts file.

Threat​

Authenticated attacker from the Internet.

Expected Remediation Time​

⌚ 15 minutes.

Score​

Default score using CVSS 3.1. It may change depending on the context of the vulnerability.

Base​

  • Attack vector: N
  • Attack complexity: L
  • Privileges required: L
  • User interaction: N
  • Scope: U
  • Confidentiality: L
  • Integrity: L
  • Availability: N

Temporal​

  • Exploit code madurity: P
  • Remediation level: O
  • Report confidence: C

Result​

  • Vector string: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N/E:P/RL:O/RC:C
  • Score:
    • Base: 5.4
    • Temporal: 4.9
  • Severity:
    • Base: Medium
    • Temporal: Medium

Code Examples​

Compliant code​

Only if the application must allow connections to insecure hosts for legacy reasons, these should be specified in the subdomains

<network-security-config>
  <domain-config cleartextTrafficPermitted="true">
    <domain includeSubdomains="true">insecure.example.com</domain>
    <domain includeSubdomains="true">insecure.cdn.example.com</domain>
  </domain-config>
</network-security-config>

Adittionally, the app should perform host validation using methods like getDefaultHostnameVerifier() or similar

SSLSocketFactory ssf = (SSLSocketFactory) SSLSocketFactory.getDefault();
SSLSocket socket = (SSLSocket) ssf.createSocket("my.host.name", 443);
socket.startHandshake();
SSLSession session = socket.getSession();

StrictHostnameVerifier verifier = new StrictHostnameVerifier();
if (!verifier.verify(session.getPeerHost(), session)) {
    // Throw some exception
}

Non compliant code​

The application allows connections to arbitrary insecure hosts

<network-security-config>
  <domain-config cleartextTrafficPermitted="false">
    <domain includeSubdomains="true">example.com</domain>
    <domain includeSubdomains="true">cdn.example2.com</domain>
  </domain-config>
  <base-config cleartextTrafficPermitted="true" />
</network-security-config>

Requirements​

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