A problem with SSL session cache in nginx was identified by Antoine
Delignat-Lavaud. It was possible to reuse cached SSL sessions in
unrelated contexts, allowing virtual host confusion attacks in some
configurations by an attacker in a privileged network position
The problem affects nginx 0.5.6 - 1.7.4 if the same shared
ssl_session_cache and/or ssl_session_ticket_key are used for multiple
The problem is fixed in nginx 1.7.5, 1.6.2.
Further details can be found in the paper by Antoine Delignat-Lavaud
et al., available at http://bh.ht.vc/vhost_confusion.pdf.