---
id: CVE-2026-53581
title: OPNsense is a FreeBSD based firewall and routing platform
summary: >-
  OPNsense is a FreeBSD based firewall and routing platform. Prior to version
  26.1.9 of opnsense/core and version 26.4_20 of BE/opnsense/core, a path
  traversal vulnerability in the NTP configuration module allows an attacker to
  overwrite a…
severity: critical
cvss: 9
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:L/A:H'
cwe:
  - CWE-22
  - CWE-73
vendor: opnsense
product: core
affected:
  - core <  26.1.9
  - core < 26.4_20
published: '2026-09-08'
updated: '2026-09-25'
sourceUpdated: '2026-09-25T14:23:59.847'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-53581'
references:
  - url: 'https://github.com/opnsense/core/security/advisories/GHSA-872g-g543-j37m'
    label: security-advisories@github.com
  - url: 'https://github.com/opnsense/core/security/advisories/GHSA-872g-g543-j37m'
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
tags:
  - nvd
  - cve.org
  - exploit-available
epss: 0.00473
epssPercentile: 0.38326
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-09-09T13:36:46.542932Z'
ingestedAt: '2026-09-08T23:13:54.646Z'
---

## Overview

OPNsense is a FreeBSD based firewall and routing platform. Prior to version 26.1.9 of opnsense/core and version 26.4_20 of BE/opnsense/core, a path traversal vulnerability in the NTP configuration module allows an attacker to overwrite arbitrary files on the system as the root user. By manipulating the GPS or PPS serial port parameter, an attacker with access to the NTP configuration can escape the intended directory and force the system to write user-controlled data to any file on the filesystem. Version 26.1.9 of opnsense/core and version 26.4_20 of BE/opnsense/core patch the issue.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.