---
id: "CVE-2026-93866"
kind: "vulnerability"
aliases: ["CVE-2026-93866"]
title: "WatchGuard Fireware OS: WebSocket integer overflow lets unauthenticated attackers write heap memory"
severity: "critical"
cvss: 9.2
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["access-portal", "firewall", "fireware-os", "infrastructure", "watchguard"]
not_affected_if: ["access-portal-disabled"]
published_at: "2026-10-27T16:17:33+00:00"
first_seen_at: "2026-10-27T16:33:07+00:00"
updated_at: "2026-10-27T16:33:55+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-93866", "first_seen_at": "2026-10-27T16:33:07+00:00"}]
---

# WatchGuard Fireware OS: WebSocket integer overflow lets unauthenticated attackers write heap memory

An integer overflow in the WebSocket handling of WatchGuard Fireware OS's Access Portal lets a remote attacker write past the end of a heap buffer. The sources do not say whether this leads to code execution, but the memory corruption is reachable without credentials.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Log in to the Fireware web UI or run the device's status command and confirm the Fireware OS version.
- Check whether the Access Portal feature is enabled in the device configuration.

## Fix

- Upgrade Fireware OS to a patched release listed in the WatchGuard advisory (version unknown from the sources).
- Disable the Access Portal feature until patched if it is not needed.

## Timeline

- 2026-10-27T16:33:07+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-93866

## From the sources

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.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_