Path Traversal in Opnsense Core
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.
Vulnerability class: Path Traversal (Directory Traversal)
CVSS v3 metric
CVSS v3 base score 9.0 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:L/A:H.
Affected products
- Opnsense Core — versions < 26.1.9, < 26.4_20
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM)
Frequently asked questions
- What is CVE-2026-53581?
- CVE-2026-53581 is a critical-severity vulnerability in Opnsense Core, classified under Path Traversal. CVSS score: 9.0/10. Published 2026-09-08.
- How severe is CVE-2026-53581?
- Critical severity. CVSS v3 base score is 9.0 out of 10.