All vulnerabilities
CVE-2026-58391GHSA-2xrm-p255-p43h

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

opnsense core
CVSS
5.4Medium
ExploitationPublic exploit codeCISA's assessment says proof of concept code is public, assessed 20 Oct 2026. Not in the KEV catalogCISA via CVE List
Exploit odds (EPSS)0.21%Chance of exploitation activity in the next 30 days, higher than 11% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed in26.1.11Also 26.4.1p1GitHub
Published15 Oct 2026Updated 20 Oct 2026CVE List

What fixes it

A fixed version on one release line is not the upgrade target for every line. Check your exact version and any vendor backports.

Description

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.

Text from CVE List

Affected versions 2

  • coreaffected: < 26.1.11CVE List
  • core<= 26.1.10, <= 26.4.1GitHub

References 4