CVE-2026-81820 Flowintel HTML Injection in MISP Case History Timeline via Crafted Object Attributes
Attackers can inject malicious HTML into MISP case timelines via crafted object attributes, potentially leading to script execution or UI manipulation.
- 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-2026-81820?
CVE-2026-81820 is a medium-severity cross-site scripting vulnerability in flowintel, published on 27 Aug 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 Flowintel construct timeline HTML using attacker-controllable MISP object fields such as:
* object UUID;
* object name;
* attribute value;
* attribute type;
* comment;
* first/last seen values;
* IDS flag.
Those values were concatenated directly into HTML strings before rendering. The upstream commit explicitly states that DOMPurify removed XSS vectors but still allowed other HTML elements, such as forms, through.
The fix replaces direct string interpolation with DOM construction via document.createElement() and assigns all attacker-controlled values using textContent. The headline is similarly converted to escaped HTML through a temporary element.
Version impacted =>3.3.0
Weakness: CWE-79
Which versions are affected by CVE-2026-81820?
How do I fix CVE-2026-81820?
No fix has been published for CVE-2026-81820 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-2026-81820 being exploited?
There is no known exploitation of CVE-2026-81820 in the wild and no public exploit code.
Sources
Also known as GHSA-cv7j-9q69-fxh4.