The remote host is missing an update to nginx announced via advisory DSA 2434-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%202434-1

Matthew Daley discovered a memory disclosure vulnerability in nginx. In previous versions of this web server, an attacker can receive the content of previously freed memory if an upstream server returned a specially crafted HTTP response, potentially exposing sensitive information. For the stable distribution (squeeze), this problem has been fixed in version 0.7.67-3+squeeze2. For the unstable distribution (sid), this problem has been fixed in version 1.1.17-1. We recommend that you upgrade your nginx packages.