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Hashtable Collisions

This module uses a denial-of-service (DoS) condition appearing in a variety of programming languages. This vulnerability occurs when storing multiple values in a hash table and all values have the same hash value. This can cause a web server parsing the POST parameters issued with a request into a hash table to consume hours of CPU with a single HTTP request. Currently, only the hash functions for PHP and Java are implemented. This module was tested with PHP + httpd, Tomcat, Glassfish and Geronimo. It also generates a random payload to bypass some IDS signatures.

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Module Name



  • Alexander Klink
  • Julian Waelde
  • Scott A. Crosby
  • Dan S. Wallach
  • Krzysztof Kotowicz
  • Christian Mehlmauer <FireFart [at]>




Module Options

To display the available options, load the module within the Metasploit console and run the commands 'show options' or 'show advanced':

msf > use auxiliary/dos/http/hashcollision_dos msf auxiliary(hashcollision_dos) > show actions ...actions... msf auxiliary(hashcollision_dos) > set ACTION <action-name> msf auxiliary(hashcollision_dos) > show options and set options... msf auxiliary(hashcollision_dos) > run

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