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MEDIUM · 6.7

CVE-2026-4266

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...

Vulnerability 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.

CVSS Score

6.7

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
Attack Vector
LOCAL
Attack Complexity
LOW
Privileges Required
HIGH
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
HIGH

Affected Products

VendorProductVersions
WatchguardFireware>= 2025.1, < 2026.2
WatchguardFirebox M295-
WatchguardFirebox M395-
WatchguardFirebox M495-
WatchguardFirebox M595-
WatchguardFirebox M695-
WatchguardFirebox T115-W-
WatchguardFirebox T125-
WatchguardFirebox T125-W-
WatchguardFirebox T145-
WatchguardFirebox T145-W-
WatchguardFirebox T185-
WatchguardFirebox Cloud-
WatchguardFirebox M270-
WatchguardFirebox M290-
WatchguardFirebox M370-
WatchguardFirebox M390-
WatchguardFirebox M440-
WatchguardFirebox M4600-
WatchguardFirebox M470-

Related Weaknesses (CWE)

CWE-502

References

FAQ

What is CVE-2026-4266?

CVE-2026-4266 is a vulnerability with a CVSS score of 6.7 (MEDIUM). 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...

How severe is CVE-2026-4266?

CVE-2026-4266 has been rated MEDIUM with a CVSS base score of 6.7/10. Review the CVSS metrics above for detailed severity breakdown.

Is there a patch for CVE-2026-4266?

Check the references section above for vendor advisories and patch information. Affected products include: Watchguard Fireware, Watchguard Firebox M295, Watchguard Firebox M395, Watchguard Firebox M495, Watchguard Firebox M595.