CVE-2021-31404: Timing side channel vulnerability in UIDL request handler in Vaadin 10, 11-14, and 15-18

Severity: low (CVSS 2.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-04-23 · updated 2026-06-17
Weakness: CWE-208

Description

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

How to fix

Upgrade to a fixed version: vaadin flow 1.0.14, 2.0.0, 2.4.7, 5.0.0; Vaadin 10.0.17, 14.0.0, 14.4.7, 17.0.0. Check the vendor advisory for mitigations.

References

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