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.
- 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-2026-86440?
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
Which versions are affected by CVE-2026-86440?
It affects 1 product.
Products include 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.
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-2026-86440 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
Sources
Also known as GHSA-m9p6-76x3-7vxp.