CVE-2017-15042: Cleartext transmission of credentials in net/smtp

Background

The net/smtp package in the Go standard library provides functionality for sending emails using the Simple Mail Transfer Protocol (SMTP). It is a widely used package for SMTP client implementations in Go. The package includes support for various authentication schemes, including PLAIN. However, prior to version 1.8.4 and 1.9.1, the PLAIN authentication scheme in net/smtp did not encrypt the transmission of credentials when used on network connections without Transport Layer Security (TLS) protection. This means that passwords were sent in clear text, making them vulnerable to interception by attackers on the network.

Vulnerability Detail

The vulnerability (CVE-2017-15042) arises from the lack of encryption in the PLAIN authentication scheme of net/smtp when used on unsecured network connections. When a client uses PLAIN authentication without TLS, the password is transmitted in clear text, allowing an attacker with access to the network traffic to intercept and obtain the password. This can lead to unauthorized access to the email account and potential misuse of the compromised credentials. The vulnerability affects versions of the Go standard library prior to 1.8.4 and 1.9.1.

go get stdlib@vgo1.25.5

Workaround

If upgrading to a fixed version of the Go standard library is not immediately feasible, a workaround can be implemented by manually encrypting the network connection using TLS. This can be achieved by using the net/smtp package in conjunction with the crypto/tls package to establish a secure TLS connection before performing the authentication. Here is an example of how to implement this workaround:

package main

import (
	"crypto/tls"
	"net/smtp"
)

func main() {
	// Create a TLS configuration
	tlsConfig := &tls.Config{
		InsecureSkipVerify: true, // Skip server certificate verification
	}

	// Dial the SMTP server with a TLS connection
	conn, err := tls.Dial("tcp", "smtp.example.com:587", tlsConfig)
	if err != nil {
		// Handle error
	}

	// Create an SMTP client using the TLS connection
	client, err := smtp.NewClient(conn, "smtp.example.com")
	if err != nil {
		// Handle error
	}

	// Perform authentication and send emails
	// ...
}

Conclusion

The vulnerability (CVE-2017-15042) in the net/smtp package of the Go standard library allows for the cleartext transmission of credentials when using the PLAIN authentication scheme on unsecured network connections. This can lead to unauthorized access to email accounts and potential misuse of compromised credentials. To fix the vulnerability, it is recommended to update to a version of the Go standard library that includes the fix (1.8.4 or 1.9.1 or later). Alternatively, a workaround can be implemented by manually encrypting the network connection using TLS. For further support on vulnerability remediation, please contact DevNack.com.

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