What is CVE-2021-31408?

CVE-2021-31408 is a medium-severity vulnerability in Vaadin Flow, classified under Insufficient Session Expiration. CVSS score: 6.3/10. Published 2021-04-23.

How severe is CVE-2021-31408?

Medium severity. CVSS v3 base score is 6.3 out of 10.

Vulnerability in Vaadin Flow

CVE-2021-31408

Authentication.logout() helper in com.vaadin:flow-client versions 5.0.0 prior to 6.0.0 (Vaadin 18), and 6.0.0 through 6.0.4 (Vaadin 19.0.0 through 19.0.3) uses incorrect HTTP method, which, in combination with Spring Security CSRF protection, allows local attackers to access Fusion endpoints after the user attempted to log out.

Published 2021-04-23 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.3 (Medium). Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N.

EPSS exploit prediction

EPSS: 0.003 (23.7th percentile), scored 2026-10-19.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 24th percentile — 23.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: 0.000

Affected products

Vaadin Flow
Vaadin Flow-Client — versions 5.0.0
Vaadin — versions 18.0.0

Weakness classification (CWE)

CWE-613 — Insufficient Session Expiration

References

vaadin.com/security/cve-2021-31408 (Vendor Advisory)
github.com/vaadin/flow/pull/10577 (Patch, Third Party Advisory)

Frequently asked questions

What is CVE-2021-31408?: CVE-2021-31408 is a medium-severity vulnerability in Vaadin Flow, classified under Insufficient Session Expiration. CVSS score: 6.3/10. Published 2021-04-23.
How severe is CVE-2021-31408?: Medium severity. CVSS v3 base score is 6.3 out of 10.