Arbitrary Code Execution in handlebars

handlebars Updated 02 Oct 2025

Summary

04/09/2020

Disclosed on

HIGH

Severity

Yes i

Fix available

High

Severity

7.3

CVSS Score

GHSA-2cf5-4w76-r9qv: Arbitrary Code Execution in handlebars. Affects handlebars across 2 version ranges.

< 3.0.8 >= 4.0.0, < 4.5.2

Fixed in 3.0.8 or 4.5.2, depending on the release line you run. How to fix ↓

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Background

Handlebars is a popular templating engine for JavaScript that allows developers to build dynamic HTML templates. It provides a simple and intuitive syntax for rendering data in HTML. However, versions of handlebars prior to 3.0.8 or 4.5.2 are vulnerable to Arbitrary Code Execution. This vulnerability arises from the package's lookup helper failing to properly validate templates, enabling attackers to submit templates that execute arbitrary JavaScript in the system. This can lead to the execution of arbitrary code in a server processing Handlebars templates or on a victim's browser, effectively serving as Cross-Site Scripting (XSS).

Vulnerability Detail

The vulnerability in handlebars allows attackers to inject and execute arbitrary JavaScript code through the package's lookup helper. By submitting a specially crafted template, an attacker can exploit this vulnerability to run arbitrary code on the server or in a victim's browser. This can lead to various malicious activities, such as stealing sensitive information, modifying web content, or performing unauthorized actions on behalf of the victim. The vulnerability affects versions of handlebars prior to 3.0.8 or 4.5.2.

How To Fix

Latest published version: 4.7.10 as of 22 Oct 2026

npm install handlebars@4.7.10

Upgrading to it may include breaking changes; the versions below are the minimum fixed release for this vulnerability.

If you can't move to the latest

The minimum fixed version depends on the release line you run.

< 3.0.8 3.0.8
```
npm install handlebars@3.0.8
```
>= 4.0.0, < 4.5.2 4.5.2
```
npm install handlebars@4.5.2
```

Tip — Not sure which release line you're on? Vulert can find the fix for the version you are using. Scan free →

Workaround

There is no known workaround for this vulnerability. It is crucial to update to the fixed versions of handlebars to mitigate the risk of arbitrary code execution.

Conclusion

The vulnerability in handlebars allows for Arbitrary Code Execution, enabling attackers to inject and execute arbitrary JavaScript code. To mitigate this risk, it is essential to update to the fixed versions of handlebars (3.0.8, 4.5.2, or later). Regularly reviewing and updating dependencies is a good practice to ensure the security of your application. For further support on vulnerability remediation, you can reach out to DevNack.com.

See every vulnerability recorded for handlebars →

FAQ

What is handlebars?

Handlebars is a templating engine for JavaScript that allows developers to build dynamic HTML templates. It provides a simple and intuitive syntax for rendering data in HTML.

What is Arbitrary Code Execution?

Arbitrary Code Execution refers to the ability of an attacker to execute arbitrary code on a target system. In the case of handlebars, this vulnerability allows attackers to inject and execute arbitrary JavaScript code through the package's lookup helper.

What are the potential consequences of this vulnerability?

The consequences of this vulnerability can be severe. Attackers can use it to steal sensitive information, modify web content, or perform unauthorized actions on behalf of the victim. It can also lead to Cross-Site Scripting (XSS) attacks, compromising the security and integrity of the affected system.

Which versions of handlebars are affected?

Versions of handlebars prior to 3.0.8 or 4.5.2 are vulnerable to this Arbitrary Code Execution vulnerability.

How can I protect my application from this vulnerability?

To protect your application, it is crucial to update the handlebars package to version 3.0.8, 4.5.2, or any later secure release. Regularly reviewing and updating your dependencies is also recommended to ensure the use of secure and up-to-date packages.