High 8.4Published Mar 30, 2026

CVE-2026-4266WatchGuard Firebox Insecure Deserialization in Fireware Access Portal

Updated under an hour ago (Oct 27, 2026, 1:30 AM ET)

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It affects WatchGuard Fireware OS and 1 other product. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for WatchGuard Fireware OS

Exploited in the last 30 days

An Insecure Deserialization vulnerability in WatchGuard Fireware OS allows an attacker that has obtained write access to the local filesystem through another vulnerability to execute arbitrary code in the context of the portald user. Note, this vulnerability does not affect Firebox platforms that do not support the Access Portal feature, including the T15 and T35.

CVSS: 8.4 HIGH (v4.0, CNA)CVSS:4.0/AV:L/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Weakness (CWE): CWE-502
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: WatchGuard
NVD analysis: Analyzed
Record last updated: Aug 27, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

WatchGuard Fireware OS watchguard:fireware_os (from the name)	from 2025.1 before 2026.2; from 12.1 before 12.12	CNA record
watchguard fireware watchguard:fireware	from 2025.1 before 2026.2; from 12.1 before 12.12	NVD

References

References

https://psirt.watchguard.com/CVE-2026-4266	vendor-advisory, broken-link
https://www.watchguard.com/wgrd-psirt/advisory/wgsa-2026-00007	vendor-advisory

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.