# CVE-2026-53581 — opnsense core

> As of 2026-09-08, CVE-2026-53581 is a CRITICAL-severity vulnerability in opnsense core, CVSS v3.1 9, EPSS 0.3% (25.4th percentile). No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-53581 as of 2026-09-08; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

**Last updated:** 2026-09-08

## What is CVE-2026-53581?

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.

The record classifies CVE-2026-53581 under weakness classes [CWE-22](https://intel.threadlinqs.com/cwe/CWE-22), [CWE-73](https://intel.threadlinqs.com/cwe/CWE-73). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs high-privilege credentials, needs no user interaction, and has high impact on confidentiality, availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 27 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 9 — CRITICAL (`CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:L/A:H`)
- **EPSS (FIRST):** 0.3% probability of exploitation in the next 30 days, higher than 25.4% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 5.5/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-09-08

## Is CVE-2026-53581 being exploited?

It currently carries a trending score of 36 in the Threadlinqs vulnerability feed.

## Affected products and versions

- **opnsense**: core

## How to fix CVE-2026-53581

No vendor patch reference has been recorded for CVE-2026-53581 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-2026-53581

No threat campaign in the Threadlinqs corpus currently references CVE-2026-53581, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.

## Sources

Enriched from CVE.org, NVD, FIRST EPSS. Last verified by Threadlinqs on 2026-09-09. This product uses the NVD API but is not endorsed or certified by the NVD.

**Vendor advisory and patch**

- [github.com](https://github.com/opnsense/core/security/advisories/GHSA-872g-g543-j37m)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-53581
Full detection coverage and IOCs for threats exploiting CVE-2026-53581 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp