CVE-2026-4266

Code execution via Access Portal deserialization

Published Mar 30, 2026 · Updated Mar 30, 2026

Insecure deserialization in WatchGuard Fireware OS 12.1 through 12.11.8 and 2025.1 through 2026.1.2 allows local users to execute code. The Access Portal deserializes attacker-controlled data from the local filesystem, causing portald to execute embedded code in its own context. Exploitation requires filesystem write access obtained through another vulnerability; Firebox models without Access Portal support, including T15 and T35, are unaffected.

CVSS severity8.4
High
EPSS probability0.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Insecure deserialization in WatchGuard Fireware OS 12.1 through 12.11.8 and 2025.1 through 2026.1.2 allows local users to execute code. The Access Portal deserializes attacker-controlled data from the local filesystem, causing portald to execute embedded code in its own context. Exploitation requires filesystem write access obtained through another vulnerability; Firebox models without Access Portal support, including T15 and T35, are unaffected.

The record

CVE
CVE-2026-4266
Published
Mar 30, 2026
Updated
Mar 30, 2026
Vendor
WatchGuard Technologies, Inc.
Product
Fireware OS
Classifications
CWE-502, CAPEC-253
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Mar 30, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 30, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=12.1 <=12.11.8
  2. Affected versionversion=2025.1 <=2026.1.2

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

WatchGuard Technologies, Inc. · Fireware OSversion=12.1 <=12.11.8; version=2025.1 <=2026.1.2

Published CVSS scores

6.7NVDCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
8.4WatchGuardCVSS:4.0/AV:L/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-502Deserialization of Untrusted Data
CAPEC-253Remote Code Inclusion

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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