Firebox and Fireware OS
CVE-2026-4266: WatchGuard Firebox Insecure Deserialization in Fireware Access Portal
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.
Published
Automatic summary from the vendor's CVE record. We haven't written a full analysis of this vulnerability yet.
Affected and fixed versions
| Product / branch | Fixed in |
|---|---|
| Fireware OS (Default) 2025.1 | 2026.2 or later |
| Fireware OS (Default) 12.1 | 12.12 or later |
| Fireware OS (EUCC) 12.1 | 12.11.9 or later |
Always confirm against the vendor advisory, which lists every fixed hotfix.
What it is
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.
Exploitation
WatchGuard is not aware of any exploitation of this issue in the wild.
Sources
KEV status, EPSS score and vendor data refreshed automatically, last on 13 Oct 2026.