S5332 — Clear-text protocols should not be used

Language
C#
Type
Vulnerability
Severity
Minor
Tags
cwe, former-hotspot

Using clear-text protocols exposes data in transit to eavesdropping and man-in-the-middle attacks.

Why is this an issue?

An attacker who can observe network traffic — for example through a compromised network device, a position on the same network segment, or a cloud environment breach — can read, modify, or inject data sent over ftp, telnet, http, or unencrypted SMTP without detection. This is true even on internal or isolated networks, where insider threats or lateral movement after an initial compromise can expose unencrypted traffic. This rule raises an issue when a clear-text protocol scheme is used or when encryption is explicitly disabled for a network connection.

What is the potential impact?

Sensitive data exposure

An attacker who can intercept network traffic can read all data transmitted over clear-text connections, including credentials, session tokens, API keys, or personal data.

Data tampering

Because clear-text protocols provide no integrity protection, an attacker in a man-in-the-middle position can silently modify data in transit — redirecting users to malicious endpoints, injecting malicious content into responses, or altering commands sent to remote services.

How to fix it

Code examples

The following code uses a clear-text protocol or disables encryption for a network connection, leaving transmitted data exposed to interception.

Noncompliant code example


var urlHttp = "http://example.com";                 // Noncompliant
var urlFtp = "ftp://anonymous@example.com";         // Noncompliant
var urlTelnet = "telnet://anonymous@example.com";   // Noncompliant


using var smtp = new SmtpClient("host", 25); // Noncompliant, EnableSsl is not set
using var telnet = new MyTelnet.Client("host", port); // Noncompliant, Telnet is a clear-text protocol

Compliant solution


var urlHttps = "https://example.com";
var urlSftp = "sftp://anonymous@example.com";
var urlSsh = "ssh://anonymous@example.com";


using var smtp = new SmtpClient("host", 25) { EnableSsl = true };
using var ssh = new MySsh.Client("host", port);

Exceptions

No issue is reported for the following cases:

Resources

Documentation

Articles & blog posts

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