Skip to main content

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

CVE-2025-65026

High
9.6/10

Summary

esm.sh is a nobuild Content Delivery Network(CDN) for modern web development. The esm.sh CDN service contains a Template Literal Injection vulnerability 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.

  • LOW
  • NETWORK
  • HIGH
  • CHANGED
  • REQUIRED
  • NONE
  • HIGH
  • HIGH

CWE-79 - Cross Site Scripting

Cross-Site Scripting, commonly referred to as XSS, is the most dominant class of vulnerabilities. It allows an attacker to inject malicious code into a pregnable web application and victimize its users. The exploitation of such a weakness can cause severe issues such as account takeover, and sensitive data exfiltration. Because of the prevalence of XSS vulnerabilities and their high rate of exploitation, it has remained in the OWASP top 10 vulnerabilities for years.

References

Advisory Timeline

  • Published