# CVE-2026-90442: WatchGuard Fireware OS stack buffer overflow in certd

Source: https://junglewise.ai/threats/cve-2026-90442-a-stack-based-buffer-overflow-vulnerability-in-the-fireware-os  
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-2026-90442 · Severity: info · Published 2026-10-27

Fireware OS is the operating system that runs WatchGuard's Firebox security appliances, which protect corporate networks. An authenticated user with access to the management interface can crash the certificate management service or potentially run malicious code by sending a specially crafted request. This could disrupt security operations or allow an attacker to gain deeper system access.

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

## Quick answers

**Is CVE-2026-90442 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-90442 being exploited in the wild.

**How severe is CVE-2026-90442?** Informational severity, published 27 October 2026.

**Which products and versions are affected?** Watchguard Fireware OS Default: 2025.1-2026.4, 12.0-12.12.4; T15/T35: 12.0-12.5.22.

**Is there a fix for CVE-2026-90442?** Yes: fixed in Fireware OS 2026.4, 12.12.4, 12.5.22. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-90442 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-90442?** 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, 12.12.4, 12.5.22

## Technical details

A stack-based buffer overflow in the Fireware OS certd process (CWE-121, CWE-787) allows an authenticated attacker with management interface access to overflow a stack buffer via a specially crafted request. The vulnerability permits denial of service of the certificate service and potentially arbitrary code execution. A fix is available in Fireware OS 2026.4, 12.12.4, and 12.5.22.

## Affected products

- WatchGuard Fireware OS Default: 2025.1-2026.4, 12.0-12.12.4; T15/T35: 12.0-12.5.22

## Timeline

- 2026-10-27: disclosed

## References

- [https://psirt.watchguard.com/CVE-2026-90442](https://psirt.watchguard.com/CVE-2026-90442)

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- [WatchGuard Fireware OS stack buffer overflow in SIP proxy](https://junglewise.ai/threats/cve-2026-93857-a-stack-based-buffer-overflow-vulnerability-in-fireware-os-s-sip)