CVE-2026-13376 WatchGuard Firebox Stored Cross-Site-Scripting (XSS) Vulnerability in spamBlocker Module

What is CVE-2026-13376?

CVE-2026-13376 is a medium-severity cross-site scripting vulnerability in Watchguard Fireware, published on 2 Jul 2026. An attacker needs administrator access to exploit it, and only if a user opens a file or follows a link.

Official description

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.

Weakness: CWE-79

Which versions are affected by CVE-2026-13376?

It affects 1 product.

Products include Watchguard Fireware.

How do I fix CVE-2026-13376?

No fix has been published for CVE-2026-13376 yet. Limit exposure of the affected software until one is available.

Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.

Is CVE-2026-13376 being exploited?

There is no known exploitation of CVE-2026-13376 in the wild and no public exploit code.

Other vulnerabilities in Watchguard Fireware

• CVE-2022-26318 WatchGuard Firebox and XTM Appliances Arbitrary Code Execution Exploited Critical 9.8
• CVE-2025-14733 WatchGuard Firebox Out of Bounds Write Exploited Critical 9.3
• CVE-2025-9242 WatchGuard Firebox Out-of-Bounds Write Exploited Critical 9.3
• CVE-2022-23176 WatchGuard Firebox and XTM Privilege Escalation Exploited High 8.8
• CVE-2022-31789 Integer overflow in n/a Critical 9.8

All Watchguard Fireware vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-35hv-3mxg-g72p.