CVE-2025-65026: esm.sh CDN service has JS Template Literal Injection in CSS-to-JavaScript

Severity: critical (CVSS 9.6 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2025-11-19 · updated 2026-10-18
Weakness: CWE-94

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.

Affected products

esm-dev esm.sh: before 136 — fixed in 136

How to fix

Upgrade to a fixed version: esm-dev esm.sh 136. Check the vendor advisory for mitigations.

References

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