Improper Certificate Validation Using poplib

The Python class poplib.POP3_SSL by default creates an SSL context that does not verify the server's certificate if the context parameter is unset or has a value of None. This means that an attacker can easily impersonate a legitimate server and fool your application into connecting to it.

If you use poplib.POP3_SSL or stls without a context set, you are opening your application up to a number of security risks, including:

  • Man-in-the-middle attacks
  • Session hijacking
  • Data theft

Example

import poplib


with poplib.POP3_SSL("domain.org") as pop3:
    pop3.user("user")

Remediation

Set the value of the context keyword argument to ssl.create_default_context() to ensure the connection is fully verified.

import poplib
import ssl


with poplib.POP3_SSL(
    "domain.org",
    context=ssl.create_default_context(),
) as pop3:
    pop3.user("user")

See also

New in version 0.3.14