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Testing servers for STARTTLS command injection vulnerability

Project description

Command Injection Tester

The command-injection-tester script allows for straightforward testing of email servers for the STARTTLS command injection vulnerability in SMTP, POP3, and IMAP.


The command

python3 command-injection-tester --imap --pop3 --smtp <hostname>

tests <hostname> for the command injection in IMAP, POP3, and SMTP.


  • --help (-h): Print help message.
  • --imap: Use the IMAP protocol
  • --pop3: Use the POP3 protocol
  • --smtp: Use the SMTP protocol
  • --imap-port (-i): IMAP port to check (default: 143)
  • --pop3-port (-p): POP3 port to check (default: 110)
  • --smtp-port (-s): SMTP port to check (default: 587)
  • --quiet (-q): Be less verbose
  • --timeout (-t): Timeout in seconds to use for network sockets. Increase in case of problems (default: 2)
  • --logdir (-l): Path to log directory (default: ./logs)


The Command Injection Tester can best be tested using the Fake Mail Server:

  1. Start the Fake Mail Server:
$ sudo ./fake_mail_server setup
  1. Run this script against the server:
$ python3 command-injection-tester --imap --pop3 --smtp localhost
  1. Since the Fake Mail Server is intentionally vulnerable against the command injection, you should see Command injection here! after every protocol test.

Testing live servers should be just as easy. If connections keep timing out/the sanity test keeps failing, try increasing the timeout using the --timeout parameter.


This tool was published as part of our research on security vulnerabilities in STARTTLS:

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