BaseFortify

Publication date: 2025-11-19

Last updated on: 2025-11-20

Assigner: GitHub, Inc.

Description

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.

CVSS Scores

EPSS Scores

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Meta Information

Published

2025-11-19

Last Modified

2025-11-20

Generated

2026-07-06

AI Q&A

2025-11-19

EPSS Evaluated

2026-07-04

NVD

CVE-2025-65026

Affected Vendors & Products

Vendor	Product	Version / Range
esm.sh	cdn	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
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.

Attack-Flow Graph

Executive Summary

The vulnerability is a Template Literal Injection (CWE-94) in esm.sh's CSS-to-JavaScript module conversion. When a CSS file is requested with the ?module parameter, esm.sh converts it into a JavaScript module by embedding the CSS content inside a template literal without proper sanitization. This allows an attacker to inject malicious JavaScript code using ${...} expressions within CSS files, which executes when the module is imported by victim applications.

Impact Analysis

This vulnerability can lead to Cross-Site Scripting (XSS) attacks in browsers and Remote Code Execution (RCE) in Electron applications. An attacker can execute arbitrary JavaScript code in the context of the victim application, potentially compromising user data, session tokens, or the application environment.

Mitigation Strategies

To mitigate this vulnerability, you should upgrade esm.sh CDN service to version 136 or later, where the Template Literal Injection vulnerability has been patched.

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