CVE-2021-31404: Vaadin Flow

Low severity, CVSS 2.5. EPSS: 0.2% chance of exploitation in the next 30 days.

Non-constant-time comparison of CSRF tokens in UIDL request handler in com.vaadin:flow-server versions 1.0.0 through 1.0.13 (Vaadin 10.0.0 through 10.0.16), 1.1.0 prior to 2.0.0 (Vaadin 11 prior to 14), 2.0.0 through 2.4.6 (Vaadin 14.0.0 through 14.4.6), 3.0.0 prior to 5.0.0 (Vaadin 15 prior to 18), and 5.0.0 through 5.0.2 (Vaadin 18.0.0 through 18.0.5) allows attacker to guess a security token via timing attack.

Affected products

• Vaadin Flow: from 1.0.0, before 1.0.14 (fixed in 1.0.14); from 1.1.0, before 2.0.0 (fixed in 2.0.0); from 2.0.0, before 2.4.7 (fixed in 2.4.7); from 3.0.0, before 5.0.0 (fixed in 5.0.0); from 5.0.0, before 5.0.3 (fixed in 5.0.3)
• Vaadin Vaadin: from 10.0.0, before 10.0.17 (fixed in 10.0.17); from 11.0.0, before 14.0.0 (fixed in 14.0.0); from 14.0.0, before 14.4.7 (fixed in 14.4.7); from 15.0.0, before 17.0.0 (fixed in 17.0.0); from 18.0.0, before 18.0.6 (fixed in 18.0.6)

Published 2021-04-23. Last modified 2026-06-17.