CVE-2021-33604: Vaadin Flow-Server

Low severity, CVSS 2.5. EPSS: 0.3% chance of exploitation in the next 30 days.

URL encoding error in development mode handler in com.vaadin:flow-server versions 2.0.0 through 2.6.1 (Vaadin 14.0.0 through 14.6.1), 3.0.0 through 6.0.9 (Vaadin 15.0.0 through 19.0.8) allows local user to execute arbitrary JavaScript code by opening crafted URL in browser.

Affected products

• Vaadin Flow-Server: from 2.0.0, up to and including 2.6.1; from 3.0.0, up to and including 5.0.0; from 6.0.0, up to and including 6.0.9
• Vaadin Vaadin: from 14.0.0, up to and including 14.6.1; from 15.0.0, up to and including 18.0.0; from 19.0.0, up to and including 19.0.8

Published 2021-06-24. Last modified 2026-06-17.