# CVE-2026-86440: MISP Dashboard Button Widget Allows Stored XSS via Unsafe javascript: and Backslash URLs

> Attackers can inject malicious scripts into MISP dashboard widgets via unsafe URLs, leading to stored XSS and potential account takeover.

- **Severity:** Medium 5.1 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA: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:** 7 Sep 2026
- **Updated:** 8 Sep 2026
- **Also known as:** GHSA-m9p6-76x3-7vxp

## What is CVE-2026-86440?

CVE-2026-86440 is a medium-severity cross-site scripting vulnerability in Misp-Project Misp, published on 7 Sep 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

Affected versions of MISP insufficiently validate URLs used by dashboard widgets, particularly the Button widget.

The widget's URL is stored configuration controlled by a user. The previous renderer considered a URL safe if it appeared relative or if its parsed hostname matched the configured MISP hostname. That logic failed to reject dangerous schemes and URL forms that browsers normalize differently from PHP's URL parsing.

As a result, values such as javascript: URLs or backslash-based authority forms could reach the generated anchor's href and execute script or navigate to an attacker-controlled origin when another user interacted with the widget. The upstream commit describes the issue as:

“javascript: and backslash URLs reached the href (stored XSS)”.

The fix routes widget URLs through a shared DashboardURLValidator, rejects dangerous schemes, raw backslashes, control characters, and unauthorized absolute origins, and validates the URL both in the widget handler and renderer.

Version affected: ≤2.5.45

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation), CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2026-86440?

It affects 1 product.


Products: Misp-Project Misp.

## How do I fix CVE-2026-86440?

No fix has been published for CVE-2026-86440 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-86440 being exploited?

There is no known exploitation of CVE-2026-86440 in the wild and no public exploit code.

## Other vulnerabilities in Misp-Project Misp

- [CVE-2024-46918](https://insights.sbomify.com/CVE-2024-46918/): Missing authorization in n/a (critical 9.8)
- [CVE-2024-45509](https://insights.sbomify.com/CVE-2024-45509/): Missing authorization in n/a (critical 9.8)
- [CVE-2024-29858](https://insights.sbomify.com/CVE-2024-29858/): File upload in n/a (critical 9.8)
- [CVE-2024-29859](https://insights.sbomify.com/CVE-2024-29859/): File upload in n/a (critical 9.8)
- [CVE-2024-25674](https://insights.sbomify.com/CVE-2024-25674/): File upload in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-86440 and fix it if it is affected.

What it is: CVE-2026-86440 is a medium-severity cross-site scripting vulnerability in Misp-Project Misp, published on 7 Sep 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-86440 in the wild and no public exploit code.

Affected product: Misp-Project 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-2026-86440/ (Markdown: https://insights.sbomify.com/CVE-2026-86440/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-86440
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-86440
- OSV: https://osv.dev/vulnerability/CVE-2026-86440

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-86440/
Summaries are generated and may contain mistakes; the official description above is the record.