Exim -- RCE with root privileges in TLS SNI handler

Exim developers report:

If your Exim server accepts TLS connections, it is vulnerable. This does
not depend on the TLS libray, so both, GnuTLS and OpenSSL are affected.
The vulnerability is exploitable by sending a SNI ending in a
backslash-null sequence during the initial TLS handshake. The exploit
exists as a POC. For more details see the document qualys.mbx