ntp: write path traversal

published 2026-09-08 2 mo ago modified 2026-09-25 44 d ago also EUVD-2026-74293

cvss: 9.0; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.5%; EPSS 0.5% chance of exploitation in 30 days, percentile 41%
public exploits: 0; none known

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.

CISA SSVC

Exploitation: Proof of concept is public
Automatable: no
Technical impact: partial
Assessed: 1 mo ago (2026-09-09)

Exploit prediction

0.47% chance of exploitation in the next 30 days, higher than 41% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/opnsense/core/security/advisories/GHSA-872g-g543-j37m referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	3.1	9.0	CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:L/A:H

Affected products

opnsense core

Classification

Weakness

CWE-22 Improper Limitation of a Pathname to a Restricted Directory
CWE-73 External Control of File Name or Path

References

github.com /opnsense/core/security/advisories/GHSA-872g-g543-j37m
exploit

Sources

CVE List CVE-2026-53581
NVD CVE-2026-53581

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary