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

> Stored XSS in OPNsense firewall rules allows attackers to execute scripts in admin sessions, potentially leading to account takeover.

- **Severity:** Medium 5.4 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 15 Oct 2026
- **Updated:** 20 Oct 2026
- **Also known as:** GHSA-2xrm-p255-p43h

## What is CVE-2026-58391?

CVE-2026-58391 is a medium-severity cross-site scripting vulnerability in opnsense core, published on 15 Oct 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official 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.

Weakness: CWE-83 (Improper Neutralization of Script in Attributes in a Web Page), CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-58391?


## How do I fix CVE-2026-58391?

No fix has been published for CVE-2026-58391 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-58391 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-58391 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-58391 and fix it if it is affected.

What it is: CVE-2026-58391 is a medium-severity cross-site scripting vulnerability in opnsense core, published on 15 Oct 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-58391 exists.

Affected product: opnsense core. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-58391/ (Markdown: https://insights.sbomify.com/CVE-2026-58391/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-58391
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-58391
- OSV: https://osv.dev/vulnerability/CVE-2026-58391

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-58391/
Summaries are generated and may contain mistakes; the official description above is the record.