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CVE-2026-4266 is an insecure deserialization vulnerability in WatchGuard Fireware OS affecting the Access Portal component. Successful exploitation allows arbitrary code execution in the context of the portald user. According to the provided information, exploitation is not standalone: the attacker must already have obtained write access to the local filesystem through another vulnerability, indicating this is a chained or post-compromise code-execution issue. Affected versions are Fireware OS 12.1 through 12.11.8 and 2025.1 through 2026.1.2. Firebox platforms that do not support the Access Portal feature, including the T-15 and T-35, are not affected.
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What an attacker gets, and what they’ve been doing with it.
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No public exploit code observed for this vulnerability.
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4 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
An insecure deserialization vulnerability in WatchGuard Fireware OS that can allow arbitrary code execution as the portald user, provided the attacker already has write access to the local filesystem through another vulnerability.
An insecure deserialization vulnerability in the WatchGuard Fireware Access Portal affecting Firebox / Fireware OS installations prior to versions 2026.2 and 12.12.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.