CVE-2026-115559
imaplib STARTTLS serves plaintext bytes buffered before the handshake as if they came over TLS
Description
IMAP4.starttls() wraps the socket in TLS but leaves self._readbuf, imaplib's own read-ahead buffer, untouched. Any plaintext bytes that arrived in the same recv() as the tagged OK to STARTTLS are returned by readline() after the handshake, so the client treats them as the first responses on the protected channel. A network attacker who cannot break TLS can append forged lines after the server's OK, let the handshake complete with the real server and a valid certificate, and have the client accept the forged CAPABILITY and the forged tagged completion of the next command. This is the STARTTLS command/response injection class of CVE-2011-0411.
INFO
Published Date :
Nov. 10, 2026, 6:39 p.m.
Last Modified :
Nov. 10, 2026, 6:39 p.m.
Remotely Exploit :
No
Source :
vulncheck-cvelist-v5
Affected Products
The following products are affected by CVE-2026-115559
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
Solution
- Update the imaplib library to the latest version.
- Apply any relevant security patches provided by the vendor.
- Ensure TLS is properly configured for IMAP connections.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-115559.
| URL | Resource |
|---|---|
| https://github.com/python/cpython/pull/160370 | patch |
| https://github.com/python/cpython/issues/160369 | issue-tracking |
| https://mail.python.org/archives/list/[email protected]/thread/LVAGFOFG26QVXEM6VXXPRMMOZBHM4CVB/ | vendor-advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-115559 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-115559
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-115559 vulnerability anywhere in the article.