module

Dhclient Bash Environment Variable Injection (Shellshock)

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

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.

Authors

Stephane Chazelas
egypt egypt@metasploit.com

Platform

Unix

Architectures

cmd

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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