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."
This vulnerability carries a MEDIUM severity rating with a CVSS v3.1 score of 6.5, indicating it can be exploited remotely over the network but requires specific conditions to be met without requiring user interaction and does not require pre-existing privileges . The vulnerability impacts limited data confidentiality, integrity (unauthorized modifications), for affected systems. Impacting 1 product from python organizations running these solutions should prioritize assessment and patching.
First disclosed in 2016, this vulnerability was reported during a period defined by widespread IoT adoption challenges, mobile security concerns, and the emergence of advanced persistent threat (APT) techniques. Contemporary mitigation strategies focused on secure development practices and third-party component vetting.
2016-09-02T14:59:00.127
2025-04-12T10:46:40.837
Deferred
CVSSv3.0: 6.5 (MEDIUM)
AV:N/AC:M/Au:N/C:P/I:P/A:N
8.6
4.9
| Type | Vendor | Product | Version/Range | Vulnerable? |
|---|---|---|---|---|
| Application | python | python | 3.5.0 | Yes |
| Application | python | python | 3.5.1 | Yes |
| Application | python | python | 3.0 | Yes |
| Application | python | python | 3.0.1 | Yes |
| Application | python | python | 3.1.0 | Yes |
| Application | python | python | 3.1.1 | Yes |
| Application | python | python | 3.1.2 | Yes |
| Application | python | python | 3.1.3 | Yes |
| Application | python | python | 3.1.4 | Yes |
| Application | python | python | 3.1.5 | Yes |
| Application | python | python | 3.2.0 | Yes |
| Application | python | python | 3.2.1 | Yes |
| Application | python | python | 3.2.2 | Yes |
| Application | python | python | 3.2.3 | Yes |
| Application | python | python | 3.2.4 | Yes |
| Application | python | python | 3.2.5 | Yes |
| Application | python | python | 3.2.6 | Yes |
| Application | python | python | 3.3.0 | Yes |
| Application | python | python | 3.3.1 | Yes |
| Application | python | python | 3.3.2 | Yes |
| Application | python | python | 3.3.3 | Yes |
| Application | python | python | 3.3.4 | Yes |
| Application | python | python | 3.3.5 | Yes |
| Application | python | python | 3.3.6 | Yes |
| Application | python | python | 3.4.0 | Yes |
| Application | python | python | 3.4.1 | Yes |
| Application | python | python | 3.4.2 | Yes |
| Application | python | python | 3.4.3 | Yes |
| Application | python | python | 3.4.4 | Yes |
| Application | python | python | ≤ 2.7.11 | Yes |
SecUtils normalizes and enriches National Vulnerability Database (NVD) records by standardizing vendor and product identifiers, aggregating vulnerability metadata from both NVD and MITRE sources, and providing structured context for security teams. For python's affected products, we extract Common Platform Enumeration (CPE) data, Common Weakness Enumeration (CWE) classifications, CVSS severity metrics, and reference data to enable rapid vulnerability prioritization and asset correlation. This record contains no exploit code, proof-of-concept instructions, or attack methodologies—only defensive intelligence necessary for patch management, risk assessment, and security operations.