CVE & CISA-KEV Catalog

CVE-2016-0772

MEDIUMEPSS 96th pctl
6.5
CVSS v3
NVD

Description

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."

CWE-693Protection Mechanism Failure

How to fix

Remediation Available
python2.7Debian
Fixed in:2.7.12~rc1-1CVE-2016-0772
libpython2.7Ubuntu
Fixed in:2.7.6-8ubuntu0.3USN-3134-1
Fixed in:2.7.12-1ubuntu0~16.04.1USN-3134-1
libpython2.7-minimalUbuntu
Fixed in:2.7.6-8ubuntu0.3USN-3134-1
Fixed in:2.7.12-1ubuntu0~16.04.1USN-3134-1
libpython2.7-stdlibUbuntu
Fixed in:2.7.6-8ubuntu0.3USN-3134-1
Fixed in:2.7.12-1ubuntu0~16.04.1USN-3134-1
libpython3.4Ubuntu
Fixed in:3.4.3-1ubuntu1~14.04.5USN-3134-1
libpython3.4-minimalUbuntu
Fixed in:3.4.3-1ubuntu1~14.04.5USN-3134-1
libpython3.4-stdlibUbuntu
Fixed in:3.4.3-1ubuntu1~14.04.5USN-3134-1
libpython3.5Ubuntu
Fixed in:3.5.2-2ubuntu0~16.04.1USN-3134-1
libpython3.5-minimalUbuntu
Fixed in:3.5.2-2ubuntu0~16.04.1USN-3134-1
libpython3.5-stdlibUbuntu
Fixed in:3.5.2-2ubuntu0~16.04.1USN-3134-1
python2.7Ubuntu
Fixed in:2.7.6-8ubuntu0.3USN-3134-1
Fixed in:2.7.12-1ubuntu0~16.04.1USN-3134-1
python2.7-minimalUbuntu
Fixed in:2.7.6-8ubuntu0.3USN-3134-1
Fixed in:2.7.12-1ubuntu0~16.04.1USN-3134-1
python3.4Ubuntu
Fixed in:3.4.3-1ubuntu1~14.04.5USN-3134-1
python3.4-minimalUbuntu
Fixed in:3.4.3-1ubuntu1~14.04.5USN-3134-1
python3.5Ubuntu
Fixed in:3.5.2-2ubuntu0~16.04.1USN-3134-1
python3.5-minimalUbuntu
Fixed in:3.5.2-2ubuntu0~16.04.1USN-3134-1

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork
Attack ComplexityHigh
Privileges RequiredNone
User InteractionNone
ScopeUnchanged

Impact

ConfidentialityLow
IntegrityHigh
AvailabilityNone

CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N

Exploit Intelligence

15.03%probability of exploitation in 30 days
96thpercentile

Very high risk: more likely to be exploited than 96% of all known CVEs.

References

Third-Party Advisory1
Mailing List1

Related Vulnerabilities

Other CWE-693 (Protection Mechanism Failure) vulnerabilities, ordered by exploit likelihood. View all

CVESeverityCVSSEPSSExploitedFix
CVE-2013-2465Critical9.899%KEV + Ransom-
CVE-2024-21412High8.195%KEV + RansomFix
CVE-2013-0431Medium5.390%KEV + Ransom-
CVE-2025-40536High8.182%KEVFix
CVE-2019-1003030Critical9.976%KEV-
CVE-2025-0411High7.067%KEVFix
Embed a live status badge for CVE-2016-0772
CVE-2016-0772 severity badge

Markdown

[![CVE-2016-0772](https://tridentstack.com/cve/badge/CVE-2016-0772.svg)](https://tridentstack.com/cve/CVE-2016-0772)

HTML

<a href="https://tridentstack.com/cve/CVE-2016-0772"><img src="https://tridentstack.com/cve/badge/CVE-2016-0772.svg" alt="CVE-2016-0772"></a>

Find and fix vulnerabilities across your fleet

TridentStack Control continuously scans your Windows, macOS, and Linux fleet for known vulnerabilities, prioritizes them by severity and active exploitation, and patches them automatically.

See how it worksStart freeThis CVE lookup is free and always will be.

This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-05-06.