CVE-2026-3343: WatchGuard Firebox Reflected Cross-Site-Scripting (XSS) Vulnerability in Fireware Web UI

Severity: medium (CVSS 6.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-03-03 · updated 2026-08-10
Weakness: CWE-79

Description

A reflected cross-site scripting (XSS) vulnerability in the Fireware OS Web UI enabled execution of malicious JavaScript in the context of an authenticated management user's browser when they click on a specially crafted link.

Affected products

WatchGuard Fireware OS: from 12.7 before 12.11.8; from 2025.1 before 2026.1.2 — fixed in 12.11.8, 2026.1.2

How to fix

Upgrade to a fixed version: WatchGuard Fireware OS 12.11.8, 2026.1.2. Check the vendor advisory for mitigations.

References

https://psirt.watchguard.com/CVE-2026-3343
https://www.watchguard.com/wgrd-psirt/advisory/wgsa-2026-00004

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