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CriticalVulnerabilityCVE-2026-93866updated 27 Oct 2026, 19:35 UTC

WatchGuard Fireware OS: remote attacker can corrupt memory via Access Portal

A flaw in the WebSocket handling of WatchGuard firewall software lets someone outside the network send a specially crafted request that corrupts the device's memory. No login is needed, and this can let an attacker take control of the firew

Official, 2 sources
SeverityCriticalCVSS 9.2 of 10
Being exploited?UnclearNo reports either way yet
Fix available?UnclearNo fixed version published in the sources yet
How sure is this?Official, 2 sourcesBacked by an official source

How the attack works simplified

  1. 1Remote attackerNo login or account needed
  2. 2Crafted requestSent to the Access Portal WebSocket
  3. 3Integer overflowSize check miscalculated in connection handling
  4. 4Heap writeWrites past the buffer's bounds
  5. ResultFirewall memory corrupted, possible takeover

What happened

An integer overflow in WebSocket connection handling in WatchGuard Fireware OS's Access Portal allows a remote, unauthenticated attacker to write beyond the bounds of a heap buffer.

Why it is dangerous: A compromised firewall sits at the network edge, so an attacker who controls it could reach internal systems and data. Organizations that expose the Access Portal to the internet are most at risk.

Are you affected?

You are affected if you run WatchGuard Fireware OS with the Access Portal feature enabled.

WatchGuard Fireware OS with Access Portal enabled (affected versions not specified in the provided material)

What to do

  1. Check whether Access Portal is enabled on your WatchGuard Fireware device and disable it if you do not need it
  2. Check WatchGuard's security advisory for the patched Fireware OS version and update as soon as it is available
  3. Limit access to the management and Access Portal interfaces to trusted networks

Timeline

  1. 27 Oct 2026, 16:17 UTC
    Publicly disclosed
  2. 27 Oct 2026, 16:17 UTC
    Reported by NVD · NVD
  3. 27 Oct 2026, 16:20 UTC
    Picked up by Zero Radar
  4. 27 Oct 2026, 19:35 UTC
    GitHub Advisory reported on it · GitHub Advisory

Sources 2 reports, oldest first

Official vendor, government CERT or advisory database

Technical details

ID
CVE-2026-93866 · GHSA-g944-9gh9-2wqp
CVSS
9.2 / 10
EPSS
0.4% chance of exploitation within 30 days
Disclosed
27 Oct 2026, 16:17 UTC
On Zero Radar
27 Oct 2026, 16:20 UTC (3 min after disclosure)
Last change
27 Oct 2026, 19:35 UTC

The plain-language parts and the attack diagram were written by an AI model (anthropic/claude-haiku-5.5) from the sources above. Facts like versions, exploitation and dates come from the sources themselves. How Zero Radar works

WatchGuard Fireware OS: remote attacker can corrupt memory via Access Portal · Zero Radar