CVE-2016-0772: Python

Medium severity, CVSS 6.5. EPSS: 14.5% chance of exploitation in the next 30 days.

The smtplib library in CPython (aka Python) before 2.7.12, 3.x before 3.4.5, and 3.5.x before 3.5.2 does not return an error when StartTLS fails, which might allow man-in-the-middle attackers to bypass the TLS protections by leveraging a network position between the client and the registry to block the StartTLS command, aka a "StartTLS stripping attack."

Affected products

• Python Python: version 3.5.0 only; version 3.5.1 only; version 3.0 only; version 3.0.1 only; version 3.1.0 only; version 3.1.1 only; …

Published 2016-09-02. Last modified 2026-06-17.