CVE-2016-0772

CVE-2016-0772 is a medium-severity vulnerability in Python with a CVSS 3.x base score of 6.5. Its EPSS exploit-prediction score of 15% places it in the 96th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-693.

Key facts

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."

Frequently asked questions

What is CVE-2016-0772?
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."
How severe is CVE-2016-0772?
CVE-2016-0772 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity high, and availability none.
Is CVE-2016-0772 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 15% (96th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2016-0772?
CVE-2016-0772 primarily affects Python. In total, 30 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2016-0772?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2016-0772 published?
CVE-2016-0772 was published on 2016-09-02 and last updated on 2026-06-17.

References

Affected products (30)

More vulnerabilities in Python

All CVEs affecting Python →

Other CWE-693 (Protection Mechanism Failure) vulnerabilities

Browse all CWE-693 (Protection Mechanism Failure) vulnerabilities →

Threat intelligence

Threat-intel indicators referencing this CVE: