Bug 2452524 (CVE-2026-33941)

Summary: CVE-2026-33941 handlebars.js: Handlebars: Arbitrary code execution via CLI precompiler input sanitization flaw
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: aazores, abuckta, cmah, dhanak, dkuc, drosa, eaguilar, ebaron, gotiwari, ibek, jcantril, jgrulich, jhorak, jkoehler, jolong, jrokos, lchilton, lphiri, mnovotny, mvyas, orabin, pjindal, rojacob, sausingh, sdawley, sfeifer, tpopela
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in Handlebars. The Handlebars command-line interface (CLI) precompiler concatenates user-controlled strings, such as template file names and CLI options, directly into the generated JavaScript without proper escaping or sanitization. An attacker capable of influencing these inputs can inject arbitrary JavaScript code. This can lead to arbitrary code execution when the generated JavaScript bundle is loaded in a Node.js environment or a web browser.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Bug Depends On: 2452597, 2452620, 2452625, 2452630, 2452634, 2452645, 2452660, 2452600, 2452605, 2452639, 2452642, 2452649, 2452655, 2452658, 2452662    
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Description OSIDB Bzimport 2026-03-27 22:03:18 UTC 
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.