CVE-2020-35217 is a high-severity (CVSS 8.8) Cross-Site Request Forgery (CSRF) vulnerability in io.vertx:vertx-web. A fix is available for io.vertx:vertx-web — see the affected versions and patch details below.
Cross-Site Request Forgery in Vert.x-Web framework
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
io.vertx:vertx-web☕io.vertx:vertx-web☕io.vertx:vertx-web☕io.vertx:vertx-webReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | io.vertx:vertx-web | ≥ 4.0.0-milestone1&&< 4.0.0-milestone5 | 4.0.0-milestone5io.vertx:vertx-web:4.0.0-milestone5 |
| ☕Maven | io.vertx:vertx-web | ≥ 4.0.0-milestone2&&< 4.0.0-milestone5 | 4.0.0-milestone5io.vertx:vertx-web:4.0.0-milestone5 |
| ☕Maven | io.vertx:vertx-web | ≥ 4.0.0-milestone3&&< 4.0.0-milestone5 | 4.0.0-milestone5io.vertx:vertx-web:4.0.0-milestone5 |
| ☕Maven | io.vertx:vertx-web | ≥ 4.0.0-milestone4&&< 4.0.0-milestone5 | 4.0.0-milestone5io.vertx:vertx-web:4.0.0-milestone5 |
Affected Products
vert.x-webeclipseDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.vertx:vertx-web, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update io.vertx:vertx-web to 4.0.0-milestone5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-35217 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Frequently Asked Questions
Is CVE-2020-35217 in your dependencies?
Find it across Maven, including transitive dependencies.