POP3 Cleartext Credentials Transmission Discovered



The Post Office Protocol version 3 (POP3) is a widely used protocol for retrieving emails from a mail server. When a remote host runs a POP3 backend program that allows plaintext entries over unencrypted connections, sensitive information such as usernames and passwords is transmitted without encryption. In this scenario, a malicious actor sniffing the network can capture the sensitive information transmitted over POP3 using USER, AUTH PLAIN, and AUTH LOGIN commands. The interception of this information can lead to unauthorized access to accounts. This can also lead to phishing attacks, as attackers can use this vulnerability to manipulate users.


Cleartext transmission of credentials in POP3 means that usernames and passwords are sent over the network without encryption. This allows attackers to sniff and intercept users' sensitive information over the network. Malicious threat actors can intercept and exploit these credentials to gain unauthorized access to user accounts and potentially compromise other systems or sensitive data.

The transmission of credentials in cleartext can enable attackers to perform unauthorized access to user accounts. Once the credentials are intercepted, attackers can easily abuse them to gain unauthorized access to sensitive information, personal data, or confidential communications.

Cleartext transmission of credentials violates data privacy regulations. It puts individuals and organizations at risk of non-compliance with data protection standards, such as the General Data Protection Regulation (GDPR) or other applicable regulations.


Use secure versions of the POP3 protocol such as POP3 over SSL/TLS (POP3S) to ensure that credentials are transmitted over an encrypted channel.

Enforce the use of strong passwords and implement multi-factor authentication (MFA) for POP3 access.

Ensure that the POP3 server only allows encrypted communication and rejects unencrypted connections.

Regularly review logs to identify anomalies and take appropriate actions.





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