CVE-2020-36321: Directory traversal in development mode handler in Vaadin 14 and 15-17

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.2% 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-22

Description

Improper URL validation in development mode handler in com.vaadin:flow-server versions 2.0.0 through 2.4.1 (Vaadin 14.0.0 through 14.4.2), and 3.0 prior to 5.0 (Vaadin 15 prior to 18) allows attacker to request arbitrary files stored outside of intended frontend resources folder.

Affected products

vaadin flow: from 2.0.0 before 2.4.2; from 3.0.0 before 5.0.0 — fixed in 2.4.2, 5.0.0
Vaadin: from 14.0.0 before 14.4.3; from 15.0.0 before 18.0.0 — fixed in 14.4.3, 18.0.0

How to fix

Upgrade to a fixed version: vaadin flow 2.4.2, 5.0.0; Vaadin 14.4.3, 18.0.0. Check the vendor advisory for mitigations.

References

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