CVE-2021-41038: Improper Verification of Communication Channel in @theia/plugin-ext
Summary
CVE-2021-41038: Improper Verification of Communication Channel in @theia/plugin-ext. Affects @theia/plugin-ext versions < 1.18.0. Fixed in 1.18.0. How to fix ↓
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Background
The @theia/plugin-ext component is a part of Eclipse Theia, an open-source cloud and desktop IDE platform. It provides extension points and APIs for developing plugins and extensions for Theia. The plugin-ext package allows developers to create webviews within Theia applications, which can display external web content. These webviews can communicate with the host application using postMessage().
Vulnerability Detail
The vulnerability (CVE-2021-41038) exists in versions of the @theia/plugin-ext component prior to 1.18.0. It stems from improper verification of the communication channel between the webview and the host application. An attacker can exploit this vulnerability by hijacking the postMessage() function to inject malicious content into the webview. This can lead to various security risks, such as cross-site scripting (XSS) attacks, data theft, or unauthorized access to sensitive information within the webview.
How To Fix
Latest published version: 1.76.0 as of 22 Oct 2026
npm install @theia/plugin-ext@1.76.0Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.
If you need the minimum change
1.18.0
This is the first release that contains the fix.
npm install @theia/plugin-ext@1.18.0Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
There is no specific workaround mentioned for this vulnerability. Updating to the fixed version is the recommended solution.
Conclusion
The vulnerability (CVE-2021-41038) in the @theia/plugin-ext component allows for the hijacking of webview contents via postMessage(). It is crucial to update to version 1.18.0 or later to mitigate this vulnerability. Failure to do so may result in potential security risks, including cross-site scripting (XSS) attacks and unauthorized access to sensitive information within the webview. For further support and assistance in vulnerability remediation, please contact DevNack.com.
See every vulnerability recorded for @theia/plugin-ext →
FAQ
@theia/plugin-ext is a component of Eclipse Theia that provides extension points and APIs for developing plugins and extensions. It allows developers to create webviews within Theia applications.
postMessage() is a method that enables communication between a webview and the host application. In the context of @theia/plugin-ext, it allows the webview to send messages to the host application and vice versa.
The vulnerability can be exploited to inject malicious content into the webview, leading to security risks such as cross-site scripting (XSS) attacks, data theft, or unauthorized access to sensitive information within the webview.
To fix this vulnerability, update the @theia/plugin-ext component to version 1.18.0 or later. Make sure to update your dependencies and rebuild your application to incorporate the patched version.
No specific workaround is mentioned for this vulnerability. Updating to the fixed version is the recommended solution.
