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Medium, CVSS 4.0

Timing side channel vulnerability in endpoint request handler in Vaadin 15-19

GHSA-9h6g-6mxg-vvp4

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (com.vaadin:vaadin-bom 19.0.1, 18.0.7), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
4.0 · CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
EPSS
No dated EPSS signal available.
Source description

As published by the source; long descriptions are shortened.

Non-constant-time comparison of CSRF tokens in endpoint request handler in com.vaadin:flow-server versions 3.0.0 through 5.0.3 (Vaadin 15.0.0 through 18.0.6), and com.vaadin:fusion-endpoint version 6.0.0 (Vaadin 19.0.0) allows attacker to guess a security token for Fusion endpoints via timing attack. - https://vaadin.com/security/cve-2021-31406

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 1 · created ·

    Published from ghsa record GHSA-9h6g-6mxg-vvp4

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: GHSA-9h6g-6mxg-vvp4

Advisory: Timing side channel vulnerability in endpoint request handler in Vaadin 15-19
IDs: GHSA-9h6g-6mxg-vvp4
Record: https://patchnext.com/advisories/ghsa-9h6g-6mxg-vvp4 (revision 1, source checked 26 Oct 2026, 15:53 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.0)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: com.vaadin:vaadin-bom 19.0.1, 18.0.7. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven com.vaadin:vaadin-bom: affected >= 19.0.0, <= 19.0.0; >= 15.0.0, < 18.0.7; fixed in 18.0.7, 19.0.1

## Suggested inspection (read-only)
- Maven com.vaadin:vaadin-bom: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on com.vaadin:vaadin-bom.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-9h6g-6mxg-vvp4 (GitHub-reviewed advisory GHSA-9h6g-6mxg-vvp4 lists affected ranges: Maven com.vaadin:vaadin-bom >=19.0.0 =15.0.0 <18.0.7)

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