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Vulnerability record · CVE-2026-4266 · published 30 March 2026

CVE-2026-4266: Watchguard fireware deserialization of untrusted data vulnerability

Watchguard · Fireware

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.

8.4 CVSS 4.0 High EPSS 0.39% · top 69.5% CWE-502 · Deserialization of untrusted data
8.4CVSS 4.0 base score
0.39%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
2References
28 Aug 2026Last modified by NVD

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:4.0/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:

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://psirt.watchguard.com/CVE-2026-4266 Broken Link
https://www.watchguard.com/wgrd-psirt/advisory/wgsa-2026-00007 Vendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.8CVE-2022-26318WatchGuard Fireware OS unauthenticated remote code executionWatchGuard Firebox and XTM appliances running Fireware OS contain an unauthenticated remote code execution flaw tracked as FBX-22786. An attacker who…KEVEPSS 78%analysed9.3CVE-2025-14733WatchGuard Fireware iked out-of-bounds write allows remote code executionWatchGuard Fireware OS contains an out-of-bounds write in the iked process reachable over the network. It affects IKEv2 mobile user VPN and branch of…KEVEPSS 27%analysed9.3CVE-2025-9242WatchGuard Fireware OS iked out-of-bounds writeWatchGuard Fireware OS contains an out-of-bounds write in the iked process that can let a remote, unauthenticated attacker execute arbitrary code. It…KEVEPSS 91%analysed8.8CVE-2022-23176WatchGuard Fireware management access privilege escalationWatchGuard Firebox and XTM appliances running Fireware OS allow a remote attacker holding unprivileged credentials to obtain a privileged management …KEVEPSS 11%analysed9.8CVE-2022-31789Watchguard fireware integer overflow vulnerabilityAn integer overflow in WatchGuard Firebox and XTM appliances allows an unauthenticated remote attacker to trigger a buffer overflow and potentially e…EPSS 1.9%9.3CVE-2013-6021Watchguard fireware memory buffer overflow vulnerabilityBuffer overflow in WGagent in WatchGuard WSM and Fireware before 11.8 allows remote attackers to execute arbitrary code via a long sessionid value in…EPSS 12%9.2CVE-2026-13368Watchguard fireware use after free vulnerabilityWatchGuard Fireware OS contains a race condition leading to a use-after-free vulnerability in LDAP authentication for the Mobile User VPN with IKEv2.…EPSS 0.94%9.1CVE-2022-25361Watchguard fireware vulnerabilityWatchGuard Firebox and XTM appliances allow an unauthenticated remote attacker to delete arbitrary files from a limited set of directories on the sys…EPSS 1.3%

Source: NIST National Vulnerability Database (record CVE-2026-4266), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.