А через nginx это к апачу придёт?
http://www.apache.org/dist/httpd/CHANGES_1.3
SECURITY: core: If a request contains both Transfer-Encoding and
Content-Length headers, remove the Content-Length, mitigating some
HTTP Request Splitting/Spoofing attacks. This has no impact on
mod_proxy_http, yet affects any module which supports chunked
encoding yet fails to prefer T-E: chunked over the Content-Length
purported value. [Paul Querna, Joe Orton]
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Pavel Sokolov
http://crea70r.photosight.ru