CVE-2026-4266
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Insecure Deserialization in WatchGuard Fireware OS Enables Code Execution

Publication date: 2026-03-30

Last updated on: 2026-03-30

Assigner: WatchGuard Technologies, Inc.

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.This issue affects Fireware OS: 12.1 through 12.11.8 and 2025.1 through 2026.1.2. Note, this vulnerability does not affect Firebox platforms that do not support the Access Portal feature, including the T-15 and T-35.
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Meta Information
Published
2026-03-30
Last Modified
2026-03-30
Generated
2026-06-16
AI Q&A
2026-03-30
EPSS Evaluated
2026-06-15
NVD
CVE-2026-4266
EUVD
EUVD-2026-17079
Affected Vendors & Products
Showing 2 associated CPEs
Vendor Product Version / Range
watchguard fireware_os From 12.1 (inc) to 12.11.8 (inc)
watchguard fireware_os From 2025.1 (inc) to 2026.1.2 (inc)
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Exploitability
CWE
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KEV
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CWE ID Description
CWE-502 The product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.
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Executive Summary

CVE-2026-4266 is an Insecure Deserialization vulnerability found in the WatchGuard Fireware OS Access Portal. It allows an attacker who already has write access to the local filesystem—obtained through another vulnerability—to execute arbitrary code with the privileges of the 'portald' user.

This vulnerability affects Fireware OS versions 12.1 through 12.11.8 and 2025.1 through 2026.1.2, but does not affect Firebox platforms that do not support the Access Portal feature, such as the T-15 and T-35 models.

Impact Analysis

If exploited, this vulnerability allows an attacker to execute arbitrary code with high privileges (the 'portald' user) on the affected system. This can lead to unauthorized control over the device, potentially compromising confidentiality, integrity, and availability of the system.

Since the attacker must already have write access to the local filesystem through another vulnerability, this issue can be part of a chained attack, increasing the overall risk to the system.

Detection Guidance

There is no specific information provided about detection methods or commands to identify this vulnerability on your network or system.

Mitigation Strategies

The vulnerability has been resolved in Fireware OS versions 12.12 and 2026.2.

Since there is no available workaround, the immediate step to mitigate this vulnerability is to upgrade affected Fireware OS versions (12.1 through 12.11.8 and 2025.1 through 2026.1.2) to version 12.12 or 2026.2.

Compliance Impact

The vulnerability allows an attacker with prior write access to execute arbitrary code with high privileges, potentially compromising confidentiality, integrity, and availability of the system.

Such a compromise could lead to unauthorized access or manipulation of sensitive data, which may negatively impact compliance with standards and regulations like GDPR and HIPAA that require protection of personal and health information.

However, the provided information does not explicitly state the direct effects on compliance with these regulations.

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