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Vulnerability record · CVE-2026-33941 · published 27 March 2026

CVE-2026-33941: Handlebarsjs handlebars cross-site scripting vulnerability

Handlebarsjs · Handlebars

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.

8.2 CVSS 3.1 High EPSS 0.22% · top 88.8% CWE-79 · Cross-site scriptingCWE-94 · Code injection
8.2CVSS 3.1 base score
0.22%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
8References, 1 tagged exploit
4 Sep 2026Last modified by NVD

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.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2 Patch
https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9 Release Notes
https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-xjpj-3mr7-gcpf ExploitVendor Advisory
https://access.redhat.com/errata/RHSA-2026:10175
https://access.redhat.com/errata/RHSA-2026:34342
https://access.redhat.com/security/cve/CVE-2026-33941
https://bugzilla.redhat.com/show_bug.cgi?id=2452524
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33941.json

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-33941), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.