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.
- 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
- None listed
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).
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.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-103321 being exploited?
There is no known exploitation of CVE-2026-103321 in the wild and no public exploit code.
Sources
Also known as GHSA-w4mv-4x7w-vpvv.