OPNsense: OpenVPN Client Specific Override common_name allows path traversal in generated CSO files

published 2026-10-15 25 d ago modified 2026-10-15 24 d ago also EUVD-2026-102115

cvss: 5.9; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.4%; EPSS 0.4% chance of exploitation in 30 days, percentile 37%
public exploits: 0; none known

OPNsense is a FreeBSD based firewall and routing platform. Prior to version 26.1.11, the OpenVPN Client Specific Override common_name field accepts path traversal sequences and openvpn_csc_conf_write() concatenates the value into /var/etc/openvpn-csc/<vpnid>/<common_name> without normalization or a basename check. The affected event handlers are client_connect.php and user_pass_verify.php. An authenticated user with Client Specific Override privileges can store the traversal value, and a matching OpenVPN client-connect or authentication event causes a generated CSO file to be written outside the intended directory. The file content is generated OpenVPN configuration rather than arbitrary bytes, and practical exploitation requires the attacker to cause a matching common name or username to be processed. This issue is fixed in version 26.1.11.

Patch / fix

fixed in 1 links 2

opnsense opnsense 26.1.11

github.com/opnsense/core@3af4961 commit
github.com/opnsense/core@6101b3e commit

CISA SSVC

Exploitation: Proof of concept is public
Automatable: no
Technical impact: partial
Assessed: 24 d ago (2026-10-15)

Exploit prediction

0.43% chance of exploitation in the next 30 days, higher than 37% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/opnsense/core/security/advisories/GHSA-2m9v-p7r9-gfcw referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	3.1	5.9	CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:L

Affected products

opnsense core

Classification

Weakness

CWE-22 Improper Limitation of a Pathname to a Restricted Directory

References

Sources

CVE List CVE-2026-58393
NVD CVE-2026-58393

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.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.

Summary