Vulnerability · Published Mar 27, 2026 · Assigned by GitHub_M
CVE-2026-33941Handlebars.js has JavaScript Injection in CLI Precompiler via Unescaped Names and Options
High 8.3
In plain English
A high-severity cross-site scripting in handlebars.js from handlebars-lang. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 22% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, the Handlebars CLI precompiler (`bin/handlebars` / `lib/precompiler.js`) concatenates user-controlled strings — template file names and several CLI options — directly into the JavaScript it emits, without any escaping or sanitization. An attacker who can influence template filenames or CLI arguments can inject arbitrary JavaScript that executes when the generated bundle is loaded in Node.js or a browser. Version 4.7.9 fixes the issue. Some workarounds are available. First, validate all CLI inputs before invoking the precompiler. Reject filenames and option values that contain characters with JavaScript string-escaping significance (`"`, `'`, `;`, etc.). Second, use a fixed, trusted namespace string passed via a configuration file rather than command-line arguments in automated pipelines. Third, run the precompiler in a sandboxed environment (container with no write access to sensitive paths) to limit the impact of successful exploitation. Fourth, audit template filenames in any repository or package that is consumed by an automated build pipeline.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | node-handlebars | no fix listed | DEBIAN-CVE-2026-33941 |
| Debian:13 | node-handlebars | no fix listed | DEBIAN-CVE-2026-33941 |
| Debian:14 | node-handlebars | 3:4.7.9-1 | DEBIAN-CVE-2026-33941 |
| Ubuntu:22.04:LTS | node-handlebars | no fix listed | UBUNTU-CVE-2026-33941 |
| Ubuntu:24.04:LTS | node-handlebars | no fix listed | UBUNTU-CVE-2026-33941 |
| Ubuntu:25.10 | node-handlebars | no fix listed | UBUNTU-CVE-2026-33941 |
| Ubuntu:26.04:LTS | node-handlebars | no fix listed | UBUNTU-CVE-2026-33941 |
| Ubuntu:26.10 | node-handlebars | no fix listed | UBUNTU-CVE-2026-33941 |
| npm | handlebars | 4.7.9 | GHSA-xjpj-3mr7-gcpf |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| handlebars-lang | handlebars.js | >= 4.0.0, < 4.7.9 |
Weakness: CWE-79, CWE-94, CWE-116 · Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H
References
- https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-xjpj-3mr7-gcpf x_refsource_CONFIRM
- https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2 x_refsource_MISC
- https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9 x_refsource_MISC
- https://access.redhat.com/security/cve/CVE-2026-33941 vdb-entry, x_refsource_REDHAT
- RHBZ#2452524 issue-tracking, x_refsource_REDHAT
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33941.json x_sadp-csaf-vex
- https://access.redhat.com/errata/RHSA-2026:34342 vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:10175 vendor-advisory, x_refsource_REDHAT