CVE-2026-4266
WatchGuard Firebox Insecure Deserialization in Fireware Access Portal
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.
INFO
Published Date :
March 30, 2026, 1:16 p.m.
Last Modified :
March 30, 2026, 1:26 p.m.
Remotely Exploit :
No
Source :
5d1c2695-1a31-4499-88ae-e847036fd7e3
Affected Products
The following products are affected by CVE-2026-4266
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 4.0 | HIGH | 5d1c2695-1a31-4499-88ae-e847036fd7e3 | ||||
| CVSS 4.0 | HIGH | 5d1c2695-1a31-4499-88ae-e847036fd7e3 |
Solution
- Update WatchGuard Fireware OS to a fixed version.
- Apply the latest vendor patches.
- Restrict filesystem write access.
- Disable Access Portal if unused.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-4266.
| URL | Resource |
|---|---|
| https://www.watchguard.com/wgrd-psirt/advisory/wgsa-2026-00007 |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-4266 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-4266
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-4266 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-4266 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by 5d1c2695-1a31-4499-88ae-e847036fd7e3
Mar. 30, 2026
Action Type Old Value New Value Added 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. Added CVSS V4.0 AV:L/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CWE CWE-502 Added Reference https://www.watchguard.com/wgrd-psirt/advisory/wgsa-2026-00007