# CVE-2026-86134 — WatchGuard Fireware OS

> As of 2026-09-30, CVE-2026-86134 is a High-severity (band derived from the CVSS v4.0 score, not stated by the CNA) vulnerability in WatchGuard Fireware OS, CVSS v4.0 8.7, EPSS 0.4% (34.2th percentile). Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2026-86134, most recently “WatchGuard Fireware OS Critical Code Injection Vulnerability in BOVPN over TLS Client (CVE-2026-86131)”.

**Last updated:** 2026-09-30

## What is CVE-2026-86134?

A NULL pointer dereference vulnerability in the WatchGuard Fireware OS authentication process allows a remote, unauthenticated attacker to crash the management daemon by sending a specially request to the login interface, resulting in a denial of service.

The record classifies CVE-2026-86134 under weakness class [CWE-476](https://intel.threadlinqs.com/cwe/CWE-476). 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 5 days ago.

## Severity and exploitation probability

- **CVSS v4.0 base score:** 8.7 — High (derived from score) (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **EPSS (FIRST):** 0.4% probability of exploitation in the next 30 days, higher than 34.2% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 5.7/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-09-30

## Is CVE-2026-86134 being exploited?

No public exploitation evidence for CVE-2026-86134 is recorded in the sources Threadlinqs tracks — CISA KEV, Exploit-DB, public proof-of-concept repositories and ProjectDiscovery Nuclei — as of 2026-09-30. That is an absence of evidence in those feeds, not a guarantee that the vulnerability is unexploited.

## Affected products and versions

- [WatchGuard](https://intel.threadlinqs.com/vendors/watchguard): Fireware OS

## How to fix CVE-2026-86134

No vendor patch reference has been recorded for CVE-2026-86134 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-86134

1 tracked threat in the Threadlinqs corpus references CVE-2026-86134, either in the campaign’s CVE list or as an indicator on the campaign record.

- [WatchGuard Fireware OS Critical Code Injection Vulnerability in BOVPN over TLS Client (CVE-2026-86131)](https://intel.threadlinqs.com/threat/TL-2026-2813) — CRITICAL · 2026-09-30

## Sources

Enriched from CVE.org, NVD, FIRST EPSS. Last verified by Threadlinqs on 2026-10-02. This product uses the NVD API but is not endorsed or certified by the NVD.

**Vendor advisory and patch**

- [psirt.watchguard.com — vendor advisory](https://psirt.watchguard.com/CVE-2026-86134)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-86134
Full detection coverage and IOCs for threats exploiting CVE-2026-86134 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp