# CVE-2026-103594: WatchGuard Fireware OS stack buffer overflow in WireGuard configuration

Source: https://junglewise.ai/threats/cve-2026-103594-a-stack-based-buffer-overflow-vulnerability-in-fireware-os-s  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-27. Updated: 2026-10-27  
License: CC BY 4.0 with a link back

CVE-2026-103594 · Severity: info · Published 2026-10-27

Fireware OS is a firewall operating system that protects corporate networks through the Firebox device. A buffer overflow vulnerability in WireGuard configuration processing allows an attacker with man-in-the-middle access to the cloud connection to crash the device (denial of service) or execute arbitrary code, potentially compromising network security and enabling lateral movement within the organization.

Technologies: [Watchguard Fireware OS](https://junglewise.ai/threats/technologies/fireware-os). Vendors: [Watchguard](https://junglewise.ai/threats/vendors/watchguard).

## Quick answers

**Is CVE-2026-103594 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-103594 being exploited in the wild.

**How severe is CVE-2026-103594?** Informational severity, published 27 October 2026.

**Which products and versions are affected?** Watchguard Fireware OS 2026.2 before 2026.4; 12.12 before 12.12.4.

**Is there a fix for CVE-2026-103594?** Yes: fixed in Fireware OS 2026.4, Fireware OS 12.12.4. Until then: This vulnerability only affects Firebox deployments configured as FireCloud Gateway devices. Organizations should restrict network access to cloud communication channels or disable FireCloud Gateway functionality until patching is completed. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-103594 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-103594?** Check whether you run Watchguard Fireware OS at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in Fireware OS 2026.4, Fireware OS 12.12.4

This vulnerability only affects Firebox deployments configured as FireCloud Gateway devices. Organizations should restrict network access to cloud communication channels or disable FireCloud Gateway functionality until patching is completed.

## Technical details

A stack-based buffer overflow exists in Fireware OS's WireGuard configuration processing when handling FireCloud Gateway configuration payloads. The vulnerability requires man-in-the-middle TLS-decrypted access between the Firebox and WatchGuard Cloud, and is only exposed when the Firebox is configured as a FireCloud Gateway. An attacker can trigger denial of service or achieve remote code execution by tampering with the configuration payload.

## Affected products

- WatchGuard Fireware OS 2026.2 before 2026.4; 12.12 before 12.12.4

## Timeline

- 2026-10-27: disclosed

## References

- [https://psirt.watchguard.com/CVE-2026-103594](https://psirt.watchguard.com/CVE-2026-103594)

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