CVE-2026-13377: Improper Neutralization of Input During Web Page Generation (XSS or 'Cross-site Scripting') vulnerability in W

Q: How do I fix CVE-2026-13377?

fireware: upgrade to 12.12.1, 2026.2.1. Exact commands for each OS are on this page.

Q: Is CVE-2026-13377 being exploited?

CVE-2026-13377 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-13377 affect?

CVE-2026-13377 affects fireware. Severity is medium (CVSS 4.8). Improper Neutralization of Input During Web Page Generation (XSS or 'Cross-site Scripting') vulnerability in WatchGuard Fireware OS SIP Proxy module allows Stored XSS. This vulnerability is an additional unmitigated attack path for CVE-2025

Q: How urgent is CVE-2026-13377?

Priority 22/100. No elevated risk signals yet.

Routine

MEDIUM 4.8UPGRADE

CVE-2026-13377 is a medium-severity flaw (CVSS 4.8) affecting fireware. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Improper Neutralization of Input During Web Page Generation (XSS or 'Cross-site Scripting') vulnerability in WatchGuard Fireware OS SIP Proxy module allows Stored XSS. This vulnerability is an additional unmitigated attack path for CVE-2025-6947.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	4.8 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	High
User interaction	Required
EPSS exploit chance	0.3% (top 81%)
CISA exploited list	No
Weakness	CWE-79
Published	2026-07-03
Last modified	2026-10-25

Publisher (CNA): WatchGuard Technologies, Inc. · Vendor: watchguard

Last updated 2026-10-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-03 00:16 UTCPublished CVE record published
2026-10-25 21:10 UTCUpdated Record last modified

watchguard fireware UPGRADE

Affected: >= 12.0 and < 12.12.1 · >= 2025.1 and < 2026.2.1 · >= 12.5 and <= 12.5.18

Fixed in: 12.12.1, 2026.2.1

Safe to downgrade to: a release before 12.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-13377?

fireware: upgrade to 12.12.1, 2026.2.1. Exact commands for each OS are on this page.

Is CVE-2026-13377 being exploited?

CVE-2026-13377 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-13377 affect?

CVE-2026-13377 affects fireware. Severity is medium (CVSS 4.8). Improper Neutralization of Input During Web Page Generation (XSS or 'Cross-site Scripting') vulnerability in WatchGuard Fireware OS SIP Proxy module allows Stored XSS. This vulnerability is an additional unmitigated attack path for CVE-2025

How urgent is CVE-2026-13377?

Priority 22/100. No elevated risk signals yet.

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References

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