VDB-354177 · CVE-2026-4266 · wgsa-2026-00007

WatchGuard Fireware OS up to 12.11.8/2026.1.2 Access Portal deserialization

CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	CTI Interest Score Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
6.7	$0-$5k	0.00

Summaryinfo

A vulnerability was found in WatchGuard Fireware OS up to 12.11.8/2026.1.2. It has been classified as critical. Affected is an unknown function of the component Access Portal. Performing a manipulation results in deserialization. This vulnerability is reported as CVE-2026-4266. The attack requires a local approach. No exploit exists.

Detailsinfo

A vulnerability classified as critical has been found in WatchGuard Fireware OS up to 12.11.8/2026.1.2. This affects an unknown code block of the component Access Portal. The manipulation with an unknown input leads to a deserialization vulnerability. CWE is classifying the issue as CWE-502. The product deserializes untrusted data without sufficiently verifying that the resulting data will be valid. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE 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.

The weakness was disclosed by btaol as wgsa-2026-00007. The advisory is shared at watchguard.com. This vulnerability is uniquely identified as CVE-2026-4266 since 03/16/2026. The exploitability is told to be easy. An attack has to be approached locally. Additional levels of successful authentication are required for exploitation. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 08/14/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-17079). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Vendor

WatchGuard

Name

Fireware OS

Version

License

commercial

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA CVSS-B Score: 🔒
CNA CVSS-BT Score: 🔒
CNA Vector: 🔒

CVSSv3info

VulDB Meta Base Score: 6.7
VulDB Meta Temp Score: 6.7

VulDB Base Score: 6.7
VulDB Temp Score: 6.7
VulDB Vector: 🔒
VulDB Reliability: 🔍

NVD Base Score: 6.7
NVD Vector: 🔒

CVSSv2info

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Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Deserialization
CWE: CWE-502 / CWE-20
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: No

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: no mitigation known
Status: 🔍

0-Day Time: 🔒

Timelineinfo

03/16/2026 CVE reserved
03/30/2026 +13 days Advisory disclosed
03/30/2026 +0 days VulDB entry created
08/14/2026 +137 days VulDB entry last update

Sourcesinfo

Advisory: wgsa-2026-00007
Researcher: btaol
Status: Confirmed

CVE: CVE-2026-4266 (🔒)
GCVE (CVE): GCVE-0-2026-4266
GCVE (VulDB): GCVE-100-354177
EUVD: 🔒

Entryinfo

Created: 03/30/2026 15:24
Updated: 08/14/2026 16:21
Changes: 03/30/2026 15:24 (66), 03/30/2026 16:12 (1), 08/14/2026 16:21 (11)
Complete: 🔍
Cache ID: 216::103

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.