CVE-2026-13376: WatchGuard Fireware

Medium severity, CVSS 4.8. EPSS: 0.3% chance of exploitation in the next 30 days.

Improper Neutralization of Input During Web Page Generation (XSS or 'Cross-site Scripting') vulnerability in WatchGuard Fireware OS spamBlocker module allows Stored XSS. This vulnerability is an additional unmitigated attack path for CVE-2025-1071. This issue affects Fireware OS 12.0 up to and including 12.12, 12.5 up to and including 12.5.18, and 2025.1 up to and including 2026.2.

Affected products

• WatchGuard Fireware: from 12.0, before 12.12.1 (fixed in 12.12.1); from 2025.1, before 2026.2.1 (fixed in 2026.2.1); from 12.5, up to and including 12.5.18

Published 2026-07-03. Last modified 2026-08-28.