CVE-2016-0772

Severity: medium (CVSS 6.5 v3.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 15.4% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2016-09-02 · updated 2026-06-17
Weakness: CWE-693

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."

Affected products

Python: through 2.7.11; 3.5.0, 3.5.1, 3.0, 3.0.1, 3.1.0, 3.1.1 (+23)

References

http://lists.opensuse.org/opensuse-security-announce/2020-01/msg00040.html
http://rhn.redhat.com/errata/RHSA-2016-1626.html
http://rhn.redhat.com/errata/RHSA-2016-1627.html
http://rhn.redhat.com/errata/RHSA-2016-1628.html
http://rhn.redhat.com/errata/RHSA-2016-1629.html
http://rhn.redhat.com/errata/RHSA-2016-1630.html
http://www.openwall.com/lists/oss-security/2016/06/14/9
http://www.securityfocus.com/bid/91225
http://www.splunk.com/view/SP-CAAAPSV
http://www.splunk.com/view/SP-CAAAPUE
https://bugzilla.redhat.com/show_bug.cgi?id=1303647
https://docs.python.org/3.4/whatsnew/changelog.html#python-3-4-5

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