OPNsense up to 26.1.10 Firewall Rules/NAT Views filter_rule.volt cross site scripting

Summaryinfo

A vulnerability classified as problematic has been found in OPNsense up to 26.1.10. Affected by this issue is some unknown functionality of the file filter_rule.volt of the component Firewall Rules/NAT Views. This manipulation causes cross site scripting. This vulnerability is registered as CVE-2026-58391. Remote exploitation of the attack is possible. No exploit is available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in OPNsense up to 26.1.10. It has been declared as problematic. Affected by this vulnerability is some unknown processing of the file filter_rule.volt of the component Firewall Rules/NAT Views. The manipulation with an unknown input leads to a cross site scripting vulnerability. The CWE definition for the vulnerability is CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. As an impact it is known to affect integrity. The summary by CVE is:

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.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-58391 since 06/30/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation requires an enhanced level of successful authentication. It demands that the victim is doing some kind of user interaction. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1059.007 for this issue.

Upgrading to version 26.1.11 eliminates this vulnerability.

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Productinfo

Name

• OPNsense

Version

• 26.1.0
• 26.1.1
• 26.1.2
• 26.1.3
• 26.1.4
• 26.1.5
• 26.1.6
• 26.1.7
• 26.1.8
• 26.1.9
• 26.1.10

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CPE 2.2info

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