The remote host is missing an update to nginx announced via advisory DSA 1884-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%201884-1

Chris Ries discovered that nginx, a high-performance HTTP server, reverse proxy and IMAP/POP3 proxy server, is vulnerable to a buffer underflow when processing certain HTTP requests. An attacker can use this to execute arbitrary code with the rights of the worker process (www-data on Debian) or possibly perform denial of service attacks by repeatedly crashing worker processes via a specially crafted URL in an HTTP request. For the oldstable distribution (etch), this problem has been fixed in version 0.4.13-2+etch2. For the stable distribution (lenny), this problem has been fixed in version 0.6.32-3+lenny2. For the testing distribution (squeeze), this problem will be fixed soon. For the unstable distribution (sid), this problem has been fixed in version 0.7.61-3. We recommend that you upgrade your nginx packages.