Upstream [1] reports: ... A bug in nginx SMTP proxy was found, which allows an attacker in a privileged network position to inject commands into SSL sessions started with the STARTTLS command, potentially making it possible to steal sensitive information sent by clients (CVE-2014-3556). The problem affects nginx 1.5.6 - 1.7.3. The problem is fixed in nginx 1.7.4, 1.6.1. Patch for the problem can be found here: http://nginx.org/download/patch.2014.starttls.txt [1]: http://mailman.nginx.org/pipermail/nginx-announce/2014/000144.html --- src/mail/ngx_mail_smtp_handler.c +++ src/mail/ngx_mail_smtp_handler.c @@ -777,6 +777,9 @@ ngx_mail_smtp_starttls(ngx_mail_session_ ngx_str_null(&s->smtp_from); ngx_str_null(&s->smtp_to); + s->buffer->pos = s->buffer->start; + s->buffer->last = s->buffer->start; + c->read->handler = ngx_mail_starttls_handler; return NGX_OK; }