# CVE-2026-54393: MISP Overmind theme stored XSS via unvalidated homepage setting

> An authenticated user can inject JavaScript via the homepage setting in the Overmind theme, leading to script execution in other users' browsers.

- **Severity:** Medium 5.1 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 12 Jun 2026
- **Updated:** 15 Jun 2026
- **Also known as:** GHSA-4hg7-5g9q-5922

## What is CVE-2026-54393?

CVE-2026-54393 is a medium-severity cross-site scripting vulnerability in misp, published on 12 Jun 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

A stored cross-site scripting vulnerability exists in MISP when the Overmind theme is used. The setHomePage endpoint previously saved the user-controlled path value through setSettingInternal(), bypassing the normal setSetting() validation logic, including validate_homepage, which requires homepage paths to start with /. As a result, an authenticated user could store an arbitrary homepage value, including an XSS payload.

The stored value was later rendered in app/View/News/index.ctp as the href attribute of the “Continue to homepage” link without HTML escaping. This could allow execution of attacker-controlled JavaScript in the browser context of the affected MISP instance when the crafted homepage link is rendered and interacted with.

The issue is fixed by always persisting the homepage setting through setSetting(), ensuring validation and access checks are applied, and by HTML-escaping the homepage value before rendering it in the news view.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-54393?


## How do I fix CVE-2026-54393?

No fix has been published for CVE-2026-54393 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-54393 being exploited?

There is no known exploitation of CVE-2026-54393 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-54393 and fix it if it is affected.

What it is: CVE-2026-54393 is a medium-severity cross-site scripting vulnerability in misp, published on 12 Jun 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-54393 in the wild and no public exploit code.

Affected product: misp. 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-2026-54393/ (Markdown: https://insights.sbomify.com/CVE-2026-54393/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-54393
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-54393
- OSV: https://osv.dev/vulnerability/CVE-2026-54393

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-54393/
Summaries are generated and may contain mistakes; the official description above is the record.