source: http://www.securityfocus.com/bid/8697/info

Null HTTPd has been reported prone to a remotely triggered denial of service vulnerability.

The issue has been reported to present itself in the HTTP POST handling routines within the Null HTTPd server. It has been reported that a remote attacker may make a malicious HTTP POST request, specifying a 'Content-Length' value in the HTTP header and then sending data that amounts to 1 byte less that the specified Content-Length. This will reportedly leave each connection on the server in an open state. An attacker can exploit this condition to trigger a denial of service of the affected server. 

POST / HTTP/1.0
Content-Length: 10

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