CVE-2026-84942 Stored Cross-Site Scripting via Vega Expression Function Bypass in OpenSearch Dashboards
Authenticated attackers can execute arbitrary JavaScript in other users' browsers by saving crafted Vega visualizations due to improper input validation.
- 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-2026-84942?
CVE-2026-84942 is a medium-severity cross-site scripting vulnerability in AWS Amazon OpenSearch Service, published on 8 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
Improper input validation in the Vega expression function implementation in OpenSearch Dashboards allows a remote authenticated actor with dashboard write permissions to execute arbitrary JavaScript in the context of other users' browser sessions by saving a crafted Vega visualization. The checkForFunctionProperty validation routine failed to recurse into arrays of objects, allowing a function property nested inside an array to bypass validation.
Weakness: CWE-79
Which versions are affected by CVE-2026-84942?
How do I fix CVE-2026-84942?
No fix has been published for CVE-2026-84942 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-2026-84942 being exploited?
There is no known exploitation of CVE-2026-84942 in the wild and no public exploit code.
Sources
Also known as GHSA-r4c3-6c67-qqwx.