CVE-2026-4266

WatchGuard Firebox Insecure Deserialization in Fireware Access Portal

State: Published
Severity: 8.4 High
Published: Mar 30, 2026
Updated: Aug 27, 2026
Reserved: Mar 16, 2026

Description

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.

Scores

CVSS	Score	Vector	Source
4.0	8.4 High	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	WatchGuard

Weaknesses

CWE-502

Affected Products

Product	Versions
Fireware OSWatchGuard	2025.1 to before 2026.2Affected 12.1 to before 12.12Affected
Fireware OSWatchGuard	12.1 to before 12.11.9Affected

References

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

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