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CVE-2026-33937: Handlebars.js has JavaScript Injection via AST Type Confusion

March 27, 2026

Handlebars.compile() accepts a pre-parsed AST object in addition to a template string. The value field of a NumberLiteral AST node is emitted directly into the generated JavaScript without quoting or sanitization. An attacker who can supply a crafted AST to compile() can therefore inject and execute arbitrary JavaScript, leading to Remote Code Execution on the server.

References

  • github.com/advisories/GHSA-2w6w-674q-4c4q
  • github.com/handlebars-lang/handlebars.js
  • github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2
  • github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9
  • github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-2w6w-674q-4c4q
  • nvd.nist.gov/vuln/detail/CVE-2026-33937

Code Behaviors & Features

Detect and mitigate CVE-2026-33937 with GitLab Dependency Scanning

Secure your software supply chain by verifying that all open source dependencies used in your projects contain no disclosed vulnerabilities. Dependency Scanning using SBOM also detects vulnerabilities from proprietary advisories that this site does not include. Learn more about Dependency Scanning using SBOM →

Affected versions

All versions starting from 4.0.0 before 4.7.9

Fixed versions

  • 4.7.9

Solution

Upgrade to version 4.7.9 or above.

Impact 9.8 CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Learn more about CVSS

Weakness

  • CWE-843: Access of Resource Using Incompatible Type ('Type Confusion')
  • CWE-94: Improper Control of Generation of Code ('Code Injection')

Source file

npm/handlebars/CVE-2026-33937.yml

Spotted a mistake? Edit the file on GitLab.

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