CVE-2016-0772

MEDIUMNVD 6.56.5—
EchelonGraph scoreMEDIUM confidence

Score 6.5 from GitHub Security Advisory published 2022-05-14. NVD baseline CVSS 6.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Elevated
6.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 15%CVSS: 6.5Exploit: Elevated riskExposed: 0

A fix is available — apply it.

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."

CVSS v3
6.5
EG Score
6.5(medium)
EG Risk
50(Track)
EG Risk 50/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity65% × 45%
Exploitation40% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
15%
EPSS %ILE
96%
KEV
Not listed

Published

September 2, 2016

Last Modified

June 17, 2026

References (36)

Patch Availability(6)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntupython3.5-venv (3.5.2-2ubuntu0~16.04.1) @ xenial2026-05-22ubuntu
redhatpython-0:2.7.5-38.el7_22016-08-18redhat
redhatpython27-python-0:2.7.8-16.el72016-08-18redhat
redhatpython33-python-0:3.3.2-16.el72016-08-18redhat
redhatrh-python34-python-0:3.4.2-13.el72016-08-18redhat
redhatrh-python35-python-0:3.5.1-9.el72016-08-18redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(4 across 3 ecosystems)
Debian:7(2)
PackageVulnerable rangeFixed inDependents
python2.72.7.3-6, 2.7.3-6+deb7u1, 2.7.3-6+deb7u22.7.3-6+deb7u3—
python3.23.2.3-73.2.3-7+deb7u1—
Debian:11(1)
PackageVulnerable rangeFixed inDependents
python2.7—2.7.12~rc1-1—
Debian:8(1)
PackageVulnerable rangeFixed inDependents
python3.43.4.2-1, 3.4.2-1+deb8u13.4.2-1+deb8u2—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

All Vendor Advisories

(6)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 5× in last 7d / 19× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 137 total refreshes for this CVE.

  1. 2026-09-18 21:06 UTCOSV refresh
  2. 2026-09-18 19:22 UTCEPSS rescore
  3. 2026-09-17 19:21 UTCEPSS rescore
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  1. 2026-08-12 13:46 UTCEPSS rescore
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  18. 2026-07-23 01:21 UTCEG score recompute
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  57. 2026-06-23 13:30 UTCOSV refresh
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Publicly available exploits

(1 reference)

Working exploit code is in the public domain (1 Exploit-DB entry). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • Exploit-DBEDB-43500
    First seen Jul 3, 2016

    Python smtplib 2.7.11 / 3.4.4 / 3.5.1 - Man In The Middle StartTLS Stripping

    Open source ↗

Frequently asked(5)

What is CVE-2016-0772?
CVE-2016-0772 is a medium vulnerability published on September 2, 2016. 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…
When was CVE-2016-0772 disclosed?
CVE-2016-0772 was first published in the National Vulnerability Database on September 2, 2016, with the most recent update on June 17, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2016-0772 actively exploited?
CVE-2016-0772 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 15% probability of exploitation in the next 30 days, which ranks it in the top 3.5% of all scored CVEs.
What is the CVSS score of CVE-2016-0772?
CVE-2016-0772 has a CVSS v3 base score of 6.5 (NVD).
How do I remediate CVE-2016-0772?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2016-0772, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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