CVE-2020-36321: Directory Traversal in Vaadin 14 and 15-17
Summary
CVE-2020-36321: Directory traversal in development mode handler in Vaadin 14 and 15-17. Affects com.vaadin:flow-server across 2 version ranges.
>= 2.0.0, < 2.4.2
>= 3.0.0, < 5.0.0
Fixed in 2.4.2 or 5.0.0, depending on the release line you run. How to fix ↓
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Background
Vaadin is an open-source Java framework used for building modern web applications. It provides a set of user interface components and tools for creating responsive and interactive web interfaces. The com.vaadin:flow-server package is a part of Vaadin and is responsible for server-side functionality. This vulnerability affects 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).
Vulnerability Detail
The vulnerability in Vaadin allows an attacker to perform directory traversal attacks in the development mode handler. This is due to improper URL validation. By exploiting this vulnerability, an attacker can request arbitrary files that are stored outside of the intended frontend resources folder. This can lead to unauthorized access to sensitive files and potential information disclosure.
How To Fix
Latest published version: 25.3.4 as of 23 Oct 2026
Upgrading to it may include breaking changes; the versions below are the minimum fixed release for this vulnerability.
If you can't move to the latest
The minimum fixed version depends on the release line you run.
-
>= 2.0.0, < 2.4.22.4.2 -
>= 3.0.0, < 5.0.05.0.0
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Workaround
There is no known workaround for this vulnerability. It is essential to apply the recommended fix by upgrading to the fixed versions of com.vaadin:flow-server.
Conclusion
The directory traversal vulnerability in Vaadin can be exploited by attackers to access arbitrary files outside of the intended frontend resources folder. It is crucial to upgrade to the fixed versions of com.vaadin:flow-server to mitigate this vulnerability. For further support on vulnerability remediation, please contact DevNack.com.
See every vulnerability recorded for com.vaadin:flow-server →
FAQ
Vaadin is an open-source Java framework for building web applications.
com.vaadin:flow-server is a package in Vaadin that provides server-side functionality.
Directory traversal is a vulnerability that allows an attacker to access files outside of the intended directory.
This vulnerability can lead to unauthorized access to sensitive files and potential information disclosure.
To fix this vulnerability, upgrade to the fixed versions of com.vaadin:flow-server as recommended.
References
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