# CVE-2026-103321: MISP Stored Cross-Site Scripting (XSS) via Unvalidated Event Graph Preview Image

> Authenticated users can inject arbitrary JavaScript via unvalidated event graph preview images, leading to session theft or actions on behalf of victims.

- **Severity:** High 8.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:H/VA:N/SC:H/SI:H/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:** 30 Sep 2026
- **Updated:** 30 Sep 2026
- **Also known as:** GHSA-w4mv-4x7w-vpvv

## What is CVE-2026-103321?

CVE-2026-103321 is a high-severity cross-site scripting vulnerability in MISP, published on 30 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

MISP contains a stored cross-site script (XSS) vulnerability in the event graph preview feature.

The event graph preview image field was accepted and stored without server-side validation. On the client side, the stored value was rendered into an HTML img element's src attribute via string concatenation, allowing a crafted value to break out of the attribute context and inject arbitrary script.

Preconditions:

- An authenticated MISP user with the ability to create or modify an event graph entry.

- A second user (the victim) who views the event graph and triggers the preview popover.

Impact:

- Execution of arbitrary JavaScript in the victim's browser within the MISP application context.

- Potential theft of session tokens, cookies, or sensitive data accessible to the victim's browser.

- Potential for performing actions on behalf of the victim within the MISP application.

Affected: MISP versions prior to the fix (commit applied after v2.5.48).

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

## Which versions are affected by CVE-2026-103321?


## How do I fix CVE-2026-103321?

No fix has been published for CVE-2026-103321 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-103321 being exploited?

There is no known exploitation of CVE-2026-103321 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-103321 and fix it if it is affected.

What it is: CVE-2026-103321 is a high-severity cross-site scripting vulnerability in MISP, published on 30 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-2026-103321 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-2026-103321/ (Markdown: https://insights.sbomify.com/CVE-2026-103321/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-103321
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-103321
- OSV: https://osv.dev/vulnerability/CVE-2026-103321

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-103321/
Summaries are generated and may contain mistakes; the official description above is the record.