---
id: "CVE-2026-93862"
kind: "vulnerability"
aliases: ["CVE-2026-93862"]
title: "FireCluster Sync: out-of-bounds read lets cluster peer crash firewall"
severity: "high"
cvss: 7.2
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: [{"name": "Fireware OS", "fixed": ["2026.4", "12.12.4"], "affected": ">= 2025.1, < 2026.4; >= 12.0, < 12.12.4", "ecosystem": "vendor"}, {"name": "Fireware OS (T15/T35)", "fixed": ["12.5.22"], "affected": ">= 12.0, < 12.5.22", "ecosystem": "vendor"}]
ecosystems: []
tags: ["firecluster", "firewall", "fireware", "high-availability", "infrastructure", "network-appliance", "self-hosted", "watchguard"]
not_affected_if: ["isolated-cluster-interconnect", "not-clustered", "standalone-firebox", "standalone-firewall"]
published_at: "2026-10-27T16:17:32+00:00"
first_seen_at: "2026-10-27T16:33:07+00:00"
updated_at: "2026-10-27T16:36:41+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-93862", "first_seen_at": "2026-10-27T16:33:07+00:00"}, {"source": "analyst", "url": null, "first_seen_at": "2026-10-27T16:36:41+00:00"}]
---

# FireCluster Sync: out-of-bounds read lets cluster peer crash firewall

A flaw in the FireCluster Sync processing of a firewall cluster lets an attacker on the cluster interconnect send crafted traffic that repeatedly crashes the cluster synchronization process. The result is a sustained denial of service on the firewall cluster.

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

## Affected

- vendor:Fireware OS affected >= 2025.1, < 2026.4; >= 12.0, < 12.12.4 fixed 2026.4, 12.12.4
- vendor:Fireware OS (T15/T35) affected >= 12.0, < 12.5.22 fixed 12.5.22

## How to check

Check whether the Firebox is in a FireCluster (Web UI: System Status > FireCluster, or CLI 'show cluster'), then its Fireware version: vulnerable if >= 2025.1 and < 2026.4, or >= 12.0 and < 12.12.4; T15/T35: >= 12.0 and < 12.5.22. Standalone Fireboxes are not affected.

## Fix

Upgrade Fireware OS to 2026.4 (2025.1 to 2026.3 branch), 12.12.4 (12.x), or 12.5.22 (T15/T35 models). Vendor lists no workaround.

## Timeline

- 2026-10-27T16:33:07+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-93862
- 2026-10-27T16:36:41+00:00 analyst — Read WatchGuard PSIRT advisory: High 7.2 (CVSS v4.0), CWE-125, not exploited per vendor, no workaround listed, no PoC/mitigations searched; social not searched.

## Documents

- [advisory] WatchGuard PSIRT: CVE-2026-93862 Out-of-Bounds Read in FireCluster Sync https://psirt.watchguard.com/CVE-2026-93862

## From the sources

An out-of-bounds read vulnerability in the FireCluster Sync processing allows an attacker positioned on the cluster interconnect, such as a compromised cluster peer or an on-path network attacker, to repeatedly crash the firewall's cluster synchronization process by sending specially crafted network traffic, resulting in a sustained denial of service.

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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_