CVE ID: CVE-2021-38371 Date: 2021-08-10 Version(s): up to and including 4.94.2 Reporter: Damian Poddebniak, Fabian Ising, Hanno Böck, and Sebastian Schinzel Reference: https://nostarttls.secvuln.info/ Issue: Possible MitM attack on STARTTLS when Exim is *sending* email. ** The Exim developers do not consider this issue as a security problem. ** Additionally, we do not have any feedback about a successful attack ** using the scenario described below. Conditions to be vulnerable =========================== Versions up to (and including) 4.94.2 are vulnerable when *sending* emails via a connection encrypted via STARTTLS. Details ======= When Exim acting as a mail client wishes to send a message, a Meddler-in-the-Middle (MitM) may respond to the STARTTLS command by also sending a response to the *next* command, which Exim will erroneously treat as a trusted response. Source fixed by https://git.exim.org/exim.git/commit/1b9ab35f323121aabf029f0496c7227818efad14 commit 1b9ab35f323121aabf029f0496c7227818efad14 Author: Jeremy Harris Date: Thu Jul 30 20:16:01 2020 +0100 Mitigation ========== There is - beside updating the server - no known mitigation. Fix === Download and build the fixed version 4.95 or a later version (4.96 was released in June 2022).