Medium 5.4Published Oct 15, 2026

CVE-2026-58391OPNsense: Stored XSS in Firewall Rules/NAT pages via a HTML-attribute breakout

Updated under an hour ago (2026-10-19 08:23 UTC)

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Exploited in the last 30 days

OPNsense is a FreeBSD based firewall and routing platform. Prior to version 26.1.11, Firewall Rules and NAT views place stored category names and alias descriptions into HTML title attributes in filter_rule.volt and nat_rule.volt without quote-safe encoding. The response layer uses ENT_NOQUOTES, so a double quote survives and closes the attribute, allowing an event-handler attribute to be added to the existing span. A user with Firewall Categories or Firewall Alias Edit privileges can store a category name or alias description; the category must be assigned to a filter or NAT rule, or the alias must be referenced by a rule source or destination, and the rule must be saved so the affected tooltip is rendered. Script then executes in the session of an administrator or other user who opens the affected Rules or NAT page. The script can access CSRF material and perform authenticated actions as the victim. This issue is fixed in version 26.1.11.

CVSS: 5.4 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Weakness (CWE): CWE-79, CWE-83
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Deferred
Record last updated: Oct 15, 2026
First seen by InfoSec Signals: Oct 15, 2026

Affected products

Affected products

opnsense core opnsense:core (from the name)	before 26.1.11	CNA record

References

https://github.com/opnsense/core/security/advisories/GHSA-2xrm-p255-p43hx-refsource-confirm
https://github.com/opnsense/core/commit/5e6313f50546474031805039e209830b63b2b0e4x-refsource-misc
https://github.com/opnsense/core/commit/fb3b8a07f407ce281b1dde748706acbb0bc514cex-refsource-misc
https://hackerask.com/posts/opnsensex-refsource-misc

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.