esm-dev esm.sh up to 135 CDN Service module code injection

Summaryinfo

A vulnerability labeled as critical has been found in esm-dev esm.sh up to 135. This affects an unknown function of the component CDN Service. The manipulation of the argument module results in code injection. This vulnerability is known as CVE-2025-65026. It is possible to launch the attack remotely. No exploit is available. The affected component should be upgraded.

Detailsinfo

A vulnerability classified as critical has been found in esm-dev esm.sh up to 135. Affected is an unknown part of the component CDN Service. The manipulation of the argument module with an unknown input leads to a code injection vulnerability. CWE is classifying the issue as CWE-94. The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

esm.sh is a nobuild content delivery network(CDN) for modern web development. Prior to version 136, The esm.sh CDN service contains a Template Literal Injection vulnerability (CWE-94) in its CSS-to-JavaScript module conversion feature. When a CSS file is requested with the ?module query parameter, esm.sh converts it to a JavaScript module by embedding the CSS content directly into a template literal without proper sanitization. An attacker can inject malicious JavaScript code using ${...} expressions within CSS files, which will execute when the module is imported by victim applications. This enables Cross-Site Scripting (XSS) in browsers and Remote Code Execution (RCE) in Electron applications. This issue has been patched in version 136.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2025-65026 since 11/13/2025. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1059.

Upgrading to version 136 eliminates this vulnerability. Applying the patch 87d2f6497574bf4448641a5527a3ac2beba5fd6c is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2025-198180). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Productinfo

Vendor

• esm-dev

Name

• esm.sh

Version

• 135

License

• open-source

Website

• Product: https://github.com/esm-dev/esm.sh/

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VulDB is the best source for vulnerability data and more expert information about this specific topic.

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