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Dhclient Bash Environment Variable Injection (Shellshock)

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Dhclient Bash Environment Variable Injection (Shellshock)

Disclosed
09/24/2014
Created
05/30/2018

Description

This module exploits the Shellshock vulnerability, a flaw in how the Bash shell handles external environment variables. This module targets dhclient by responding to DHCP requests with a malicious hostname, domainname, and URL which are then passed to the configuration scripts as environment variables, resulting in code execution. Due to length restrictions and the unusual networking scenario at the time of exploitation, this module achieves code execution by writing the payload into /etc/crontab and then cleaning it up after a session is created.

Author(s)

  • Stephane Chazelas
  • egypt <egypt@metasploit.com>

Platform

Unix

Architectures

cmd

Development

References

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 exploit/unix/dhcp/bash_environment
msf exploit(bash_environment) > show targets
    ...targets...
msf exploit(bash_environment) > set TARGET < target-id >
msf exploit(bash_environment) > show options
    ...show and set options...
msf exploit(bash_environment) > exploit

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