CVE-2026-33941

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.

Important: This flaw in Handlebars allows arbitrary code execution when the CLI precompiler processes untrusted inputs. An attacker who can influence template filenames or command-line arguments can inject malicious JavaScript, which executes when the generated bundle is loaded. Red Hat products utilizing the Handlebars CLI precompiler in environments where untrusted inputs are processed may be affected.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this issue, ensure all inputs to the Handlebars CLI precompiler are thoroughly validated, rejecting characters with JavaScript string-escaping significance (e.g., " , ' , ;). For automated build pipelines, configure a fixed and trusted namespace string via a configuration file rather than passing it through command-line arguments. Additionally, consider running the precompiler within a sandboxed environment, such as a container with restricted write access, to limit the potential impact of successful exploitation.