| Buffer overflow attacks are carried out by a malicious attacker sending amounts of data that the web server cannot store in a given size buffer. The eventual overflow of this buffer can overwrite system memory. Subsequently an attacker may be able to elevate privileges and take control of the server. This Apache directives limits the size of the various HTTP header sizes thereby limiting the chances for a buffer overflow.
The LimitRequestLine directive allows the server administrator to reduce or increase the limit on the allowed size of a client's HTTP request-line. Since the request-line consists of the HTTP method, URI, and protocol version, the LimitRequestLine directive places a restriction on the length of a request-URI allowed for a request on the server. A server needs this value to be large enough to hold any of its resource names, including any information that might be passed in the query part of a GET request.
This directive gives the server administrator greater control over abnormal client request behavior, which may be useful for avoiding some forms of denial-of-service attacks.