CVE-2025-65026: GO-2025-4139 - esm.sh CDN service has JS Template Literal Injection in CSS-to-JavaScript in github.com/esm-dev/esm.sh

CVE-2025-65026 · Severity: medium · CVSS 6.1 · Published 2025-11-19

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.

Technologies: github.com/esm-dev/esm.sh (Go). Vendors: Go.

Quick answers

Is CVE-2025-65026 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2025-65026 being exploited in the wild.
How severe is CVE-2025-65026?
Medium severity, with a CVSS score of 6.1, published 19 November 2025.
Which products and versions are affected?
github.com/esm-dev/esm.sh (Go) SEMVER:introduced=0,fixed=0.0.0-20251118065157-87d2f6497574.
Is there a fix for CVE-2025-65026?
Yes. github.com/esm-dev/esm.sh (Go): upgrade to 0.0.0-20251118065157-87d2f6497574 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
Am I affected by CVE-2025-65026?
Check whether you run Esm.Sh or github.com/esm-dev/esm.sh (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • github.com/esm-dev/esm.sh (Go): upgrade to 0.0.0-20251118065157-87d2f6497574 or later
    go get github.com/esm-dev/esm.sh@v0.0.0-20251118065157-87d2f6497574

Affected products

  • Esm.Sh
  • github.com/esm-dev/esm.sh (Go) SEMVER:introduced=0,fixed=0.0.0-20251118065157-87d2f6497574

Identifiers

  • CVE-2025-65026
  • GHSA-hcpf-qv9m-vfgp
  • GO-2025-4139

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