The ngx_http_parse_chunked function in http/ngx_http_parse.c in nginx 1.3.9 through 1.4.0 allows remote attackers to cause a denial of service (crash) and execute arbitrary code via a chunked Transfer-Encoding request with a large chunk size, which triggers an integer signedness error and a stack-based buffer overflow.
https://github.com/rapid7/metasploit-framework/pull/1834
http://www.securityfocus.com/bid/59699
http://security.gentoo.org/glsa/glsa-201310-04.xml
http://secunia.com/advisories/55181
http://nginx.org/download/patch.2013.chunked.txt
http://mailman.nginx.org/pipermail/nginx-announce/2013/000112.html
http://lists.fedoraproject.org/pipermail/package-announce/2013-May/105176.html