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Use of an insecure channel - Telnet


Customer information is transmitted over a channel that does not use encryption, so credentials and confidential information can be captured in plain text.


Obtain Telnet credentials after a MitM attack.


Deploy the application over an encrypted communication channel.


Anonymous attacker from adjacent network.

Expected Remediation Time

⌚ 60 minutes.


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


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


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


  • Vector string: CVSS:3.1/AV:A/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N/E:P/RL:O/RC:X
  • Score:
    • Base: 4.6
    • Temporal: 4.2
  • Severity:
    • Base: Medium
    • Temporal: Medium

Code Examples

Compliant code

The application uses an secure channel to transmit data

public static void CreateTestMessage(string server){
SmtpClient client = new SmtpClient(server);
client.UseDefaultCredentials = true;
client.EnableSsl = true;

Non compliant code

The application uses an insecure channel to transmit data

public static void CreateTestMessage(string server){
TcpClient telnet = new TcpClient("", 23);
NetworkStream telnetStream = telnet.GetStream();
StreamWriter output = new StreamWriter(telnetStream);
StreamReader input = new StreamReader(telnetStream);


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