Remote Code Execution Vulnerability in Handlebars by Handlebars.js
CVE-2026-33937
Key Information:
- Vendor
Handlebars-lang
- Status
- Vendor
- CVE Published:
- 27 March 2026
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What is CVE-2026-33937?
CVE-2026-33937 is a remote code execution vulnerability found in the Handlebars.js templating engine, a widely used library that allows developers to create semantic templates. This vulnerability affects versions 4.0.0 through 4.7.8 of Handlebars, wherein the Handlebars.compile() method can process a pre-parsed Abstract Syntax Tree (AST) object without proper validation. Specifically, a NumberLiteral node within the AST can be emitted directly into the generated JavaScript code without proper quoting or sanitization. This flaw enables attackers to inject and execute arbitrary JavaScript code on the server by supplying a crafted AST. The implications of such an exploitation can be severe, as it may allow attackers to gain unauthorized access to server resources, manipulate data, or disrupt services. Organizations relying on Handlebars for templating in their applications must address this vulnerability to safeguard against potential malicious exploits.
Potential Impact of CVE-2026-33937
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Arbitrary Code Execution: The core issue of this vulnerability is the ability for an attacker to inject and execute arbitrary JavaScript code on the server. This could lead to full control over the server environment, allowing malicious activities such as data exfiltration, server manipulation, and the deployment of further exploits.
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Data Integrity Risk: Given the nature of code execution vulnerabilities, an attacker could manipulate data processed by the server. This could lead not only to unauthorized alterations of application data but also to the creation of backdoors and persistent threats that could compromise the integrity of the system.
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Service Disruption: Exploiting this vulnerability may result in a denial of service for the affected applications. Attackers could leverage the ability to execute code to cause service outages, resource exhaustion, or to interfere with critical application functionalities, ultimately impacting business operations.
Affected Version(s)
handlebars.js >= 4.0.0, < 4.7.9
Exploit Proof of Concept (PoC)
PoC code is written by security researchers to demonstrate the vulnerability can be exploited. PoC code is also a key component for weaponization which could lead to ransomware.