WatchGuard Fireware OS: Pre-authentication heap overflow in Access Portal
Summary
An integer overflow in the WebSocket connection handling of the Access Portal in WatchGuard Fireware OS allows a remote, unauthenticated attacker to write beyond the bounds of a heap buffer. The attack works only when the Access Portal feature is enabled on the Firebox. Successful exploitation may allow code execution or a denial of service; the exact impact is not described in the sources. The Access Portal is designed to receive requests from the public Internet, so exposed devices are at risk.
Affected
- Fireware OS 2025.1 to before 2026.4 (default track)
- Fireware OS 12.0 to before 12.12.4 (default track)
- Fireware OS 12.0 to before 12.5.22 (T15/T35)
- Only Fireboxes with the Access Portal enabled are affected.
Fixed in
- Fireware OS 2026.4
- Fireware OS 12.12.4
- Fireware OS 12.5.22 (T15/T35)
Workaround
- Unknown. The vendor advisory reviewed does not describe a workaround.
- Disabling the Access Portal, where it is not needed, removes the exposure described in the advisory.
Exploitation
- WatchGuard is not aware of any exploitation of this vulnerability in the wild.
- Not listed in CISA KEV in the sources reviewed.
- No public proof-of-concept found in the sources reviewed.
Our recommendation
- Identify Fireboxes on affected Fireware OS versions and check whether the Access Portal is enabled.
- Upgrade to Fireware OS 2026.4, 12.12.4 or 12.5.22 (T15/T35) as applicable.
- If patching must wait, disable the Access Portal if it is not in use.
- Apply the other Fireware OS fixes published with this release together.
- Monitor firewall logs for unusual requests to the Access Portal until patched.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- WatchGuard PSIRT advisory CVE-2026-93866 psirt.watchguard.com
- VulDB entry 427423 vuldb.com
- Offseq radar entry CVE-2026-93866 radar.offseq.com
- NVD-mirrored record (threatint) cve.threatint.com
- WatchGuard Access Portal documentation www.watchguard.com
- Cybersecurity News: WatchGuard critical firewall flaws cybersecuritynews.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 31 Oct 2026, 03:57.
Original description (NVD)
An integer overflow vulnerability in the WebSocket connection handling used by WatchGuard Fireware OS's Access Portal allows a remote, unauthenticated attacker to write beyond the bounds of a heap buffer by sending a specially crafted request while the Access Portal feature is enabled.
NVD references (1)
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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