CVE-2016-0772

What it is

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."

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data tampering.

Exploit odds

15.4% chance of exploitation in the next 30 days (EPSS). Higher than most.

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2016-09-02 14:59 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 00:38 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 15.4% in the next 30 days (EPSS).
• Severity: 6.5 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2016-09-02 14:59 UTC

Last modified

2026-06-17 00:38 UTC

Exploit probability

15.4% · EPSS, next 30 days

Weakness

CWE-693

Record status

Modified

Affected

• Python 3.5.0
• Python 3.5.1
• Python 3.0
• Python 3.0.1
• Python 3.1.0
• Python 3.1.1
• Python 3.1.2
• Python 3.1.3

Attack profile CVSS 3.0 · 6.5

Attack vector

Network

Complexity

High

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

High

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2016-0772.md and follow it. Check whether this project is affected by CVE-2016-0772. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

Copy as ticket · More options · Status badge