Juniper SRX Firewall / EX Switch Remote Code Execution
Posted on 02 October 2023
This Metasploit module exploits a PHP environment variable manipulation vulnerability affecting Juniper SRX firewalls and EX switches. The affected Juniper devices running FreeBSD and every FreeBSD process can access their stdin by opening /dev/fd/0. The exploit also makes use of two useful PHP features. The first being auto_prepend_file which causes the provided file to be added using the require function. The second PHP function is allow_url_include which allows the use of URL-aware fopen wrappers. By enabling allow_url_include, the exploit can use any protocol wrapper with auto_prepend_file. The module then uses data:// to provide a file inline which includes the base64 encoded PHP payload. By default this exploit returns a session confined to a FreeBSD jail with limited functionality. There is a datastore option JAIL_BREAK, that when set to true, will steal the necessary tokens from a user authenticated to the J-Web application, in order to overwrite the root password hash. If there is no user authenticated to the J-Web application this method will not work. The module then authenticates with the new root password over SSH and then rewrites the original root password hash to /etc/master.passwd.
