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CVE-2026-58393: OPNsense: OpenVPN Client Specific Override common_name allows path traversal in generated CSO files

• Severity: medium (CVSS 5.9 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-15 · updated 2026-10-15
• Weakness: CWE-22

Description

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.

Affected products

• opnsense core: before 26.1.11

References

• https://github.com/opnsense/core/commit/3af496143a19153c18b2f9458b2510d58aff2b98
• https://github.com/opnsense/core/commit/6101b3e2c90482111f420a47775c14a447441a72
• https://github.com/opnsense/core/security/advisories/GHSA-2m9v-p7r9-gfcw
• https://github.com/opnsense/core/security/advisories/GHSA-2m9v-p7r9-gfcw

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