CVE-2020-35217

Cross-Site Request Forgery in Vert.x-Web framework

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.

A victim's authenticated browser session is used to submit forged requests to an application that cannot distinguish them from legitimate ones. Typical impact: state-changing actions performed as the victim without their consent.

CVE-2020-35217 has a CVSS score of 8.8 (High). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (4.0.0-milestone5); upgrading removes the vulnerable code path.

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1. What is CVE-2020-35217? CVE-2020-35217 is a high-severity cross-site request forgery (CSRF) vulnerability in io.vertx:vertx-web (maven), affecting versions = 4.0.0-milestone1. It is fixed in 4.0.0-milestone5. A victim's authenticated browser session is used to submit forged requests to an application that cannot distinguish them from legitimate ones.
2. How severe is CVE-2020-35217? CVE-2020-35217 has a CVSS score of 8.8 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of io.vertx:vertx-web are affected by CVE-2020-35217? io.vertx:vertx-web (maven) versions = 4.0.0-milestone1 is affected.
4. Is there a fix for CVE-2020-35217? Yes. CVE-2020-35217 is fixed in 4.0.0-milestone5. Upgrade to this version or later.
5. Is CVE-2020-35217 exploitable, and should I be worried? Whether CVE-2020-35217 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2020-35217 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2020-35217?
   • Upgrade io.vertx:vertx-web to 4.0.0-milestone5 or later
   • Upgrade io.vertx:vertx-web to 4.0.0-milestone5 or later
   • Upgrade io.vertx:vertx-web to 4.0.0-milestone5 or later
   • Upgrade io.vertx:vertx-web to 4.0.0-milestone5 or later

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