StartTLS Stripping Vulnerability in smtplib Library

CVE-2016-0772 · MEDIUM Severity

AV:N/AC:M/AU:N/C:P/I:P/A:N

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."

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