What is CVE-2026-13376?

CVE-2026-13376 is a medium-severity vulnerability in Watchguard Fireboxcloud, classified under Cross-site Scripting. CVSS score: 4.8/10. Published 2026-07-03.

How severe is CVE-2026-13376?

Medium severity. CVSS v3 base score is 4.8 out of 10.

XSS in Watchguard Fireboxcloud

CVE-2026-13376

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.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2026-07-03 · last modified 2026-08-28.

CVSS v3 metric

CVSS v3 base score 4.8 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.003 (17.7th percentile), scored 2026-10-08.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 18th percentile — 17.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: 0.000

Affected products

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

5d1c2695-1a31-4499-88ae-e847036fd7e3 (vendor-advisory, Vendor Advisory)
5d1c2695-1a31-4499-88ae-e847036fd7e3 (vendor-advisory)

Frequently asked questions

What is CVE-2026-13376?: CVE-2026-13376 is a medium-severity vulnerability in Watchguard Fireboxcloud, classified under Cross-site Scripting. CVSS score: 4.8/10. Published 2026-07-03.
How severe is CVE-2026-13376?: Medium severity. CVSS v3 base score is 4.8 out of 10.