CVE-2021-34435: Eclipse Theia

High severity, CVSS 8.8. EPSS: 0.6% chance of exploitation in the next 30 days.

In Eclipse Theia 0.3.9 to 1.8.1, the "mini-browser" extension allows a user to preview HTML files in an iframe inside the IDE. But with the way it is made it is possible for a previewed HTML file to trigger an RCE. This exploit only happens if a user previews a malicious file..

Affected products

• Eclipse Theia: from 0.3.9, up to and including 1.8.1

Published 2021-09-01. Last modified 2026-06-17.