CVE-2021-21316 Explained : Impact and Mitigation

A vulnerability labeled CVE-2021-21316 has been identified in less-openui5, an npm package used for building OpenUI5 themes with Less.js. The issue arises from the execution of JavaScript code in the context of the build process when processing theming resources originating from untrusted sources. This unexpected behavior poses a security risk to OpenUI5 and SAPUI5 development.

Understanding CVE-2021-21316

What is CVE-2021-21316?

less-openui5, prior to version 0.10.0, allows for the execution of JavaScript code within theming resources, potentially leading to arbitrary code execution in the development environment.

The Impact of CVE-2021-21316

The vulnerability in less-openui5 could be exploited by attackers to embed malicious JavaScript code in .less files, compromising the integrity of the build process and resulting in arbitrary code execution.

Technical Details of CVE-2021-21316

Vulnerability Description

The issue stems from the use of an older version of Less.js in less-openui5, enabling the evaluation of JavaScript code within theming resources.

Affected Systems and Versions

Less-openui5 versions earlier than 0.10.0 are impacted by this vulnerability.

Exploitation Mechanism

An attacker can hide malicious JavaScript code within .less files, which can then be executed during the theming resource processing.

Mitigation and Prevention

Immediate Steps to Take

To mitigate this vulnerability, users are strongly advised to update to version 0.10.0 of less-openui5 or newer. This version disables the Inline JavaScript feature by default.

Long-Term Security Practices

Developers should always verify the source of theming resources and avoid using files from untrusted origins to prevent similar security risks.

Patching and Updates

Stay informed about security updates and patches released for less-openui5. Regularly update to the latest versions to ensure that known vulnerabilities are addressed.