CVE-2026-115559imaplib STARTTLS serves plaintext bytes buffered before the handshake as if they came over TLS

Beschreibung

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.

Daten: CVE.org, NVD, CISA KEV, FIRST EPSS, Ubuntu. Wiedergegeben wie in der Quelle, auf Englisch.

Betroffene Produkte und Versionen

Referenzen und Patches

• https://github.com/python/cpython/pull/160370 patch
• https://github.com/python/cpython/issues/160369 issue-tracking
• https://mail.python.org/archives/list/security-announce@python.org/thread/LVAGFOFG26QVXEM6VXXPRMMOZBHM4CVB/ vendor-advisory