CVE-2026-4266: WatchGuard Fireware

Medium severity, CVSS 6.7. EPSS: 0.4% chance of exploitation in the next 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.

Affected products

• WatchGuard Fireware: from 2025.1, before 2026.2 (fixed in 2026.2); from 12.1, before 12.12 (fixed in 12.12)

Published 2026-03-30. Last modified 2026-08-28.