Understanding CVE-2025-9242 – What the WatchGuard Firebox Vulnerability Means & How to Protect Yourself

What Is CVE-2025-9242?

CVE-2025-9242 is a critical vulnerability in the WatchGuard Firebox Fireware OS identified in advisory WGSA-2025-00015. 

• It’s an Out-of-Bounds Write flaw in the iked process, which is part of WatchGuard’s implementation of IKEv2 (Internet Key Exchange version 2). 

• Because of this vulnerability, a remote unauthenticated attacker could potentially execute arbitrary code on a Firebox device. 

• The vulnerability affects both mobile user VPNs with IKEv2 and branch office VPNs using IKEv2 when those VPNs are configured with a dynamic gateway peer. 

Which Devices and Versions Are Affected

The issue spans a broad range of Firebox devices and Fireware OS versions. Some of the affected versions include:

• Fireware OS 11.10.2 up to 11.12.4_Update1 

• Fireware OS 12.0 up through 12.11.3 

• OS version 2025.1 

It also affects multiple hardware models: Firebox T15, T35; various “12.x” T-series, Firebox Cloud, NV5, V models etc.

WatchGuard Firebox T15

Severity & Impact

• The CVSS score is 9.3 / Critical. 

• Because it allows a remote unauthenticated attacker to write out of bounds and potentially execute arbitrary code, the risk is high. 

• Even if certain vulnerable configurations have been deleted (e.g. dynamic gateway peer VPNs), Fireboxes may still remain vulnerable if a branch-office VPN to a static gateway peer is still configured. 

What Should You Do: Mitigations & Remediation

1. Patch as Soon as Possible

WatchGuard has released fixed versions of Fireware OS that resolve this vulnerability. Some fixed versions include:

• 2025.1 → 2025.1.1 

• 12.x → 12.11.4 

• For Firebox T-series and other models, other corresponding patches have also been released. 

2. Workaround (if you can’t immediately patch)

If you can’t immediately upgrade:

• Limit or disable branch office VPNs using IKEv2 with dynamic gateway peers.

• Follow WatchGuard’s guidance for “Secure Access to Branch Office VPNs that Use IPSec and IKEv2” until the patch is applied. 

3. Audit Configurations

• Verify whether your Firebox devices have been configured with mobile user VPN with IKEv2 or branch office VPNs with IKEv2 and dynamic gateway peers.

• Even if those configurations were removed in the past, check if there are static gateway peer configs that might still leave a device exposed.

4. Review Security Posture

• Ensure VPN endpoints are hardened and monitored.

• Use network segmentation and limit access only to necessary systems.

• Apply least privilege principles: only allow what is necessary for the VPN connections.

Why This Matters

VPNs are a critical piece of many organizations’ infrastructure. A vulnerability like CVE-2025-9242 has potential to grant access to internal network resources if a Firebox is compromised. The broad set of affected versions and devices increases the urgency.

Conclusion

CVE-2025-9242 is a serious vulnerability in WatchGuard Firebox devices. If you manage any Firebox appliance:

1. Check if your version is affected

2. Patch to a resolved version immediately

3. If unable to patch right away, apply the workaround

4. Audit your VPN configurations and access controls

Keeping your firewall and VPN infrastructure up-to-date is essential for maintaining overall network security.