CVE-2026-106446

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BaseFortify

Publication date: 2026-10-06

Last updated on: 2026-10-07

Assigner: GitHub, Inc.

Description

Handlebars provides the power necessary to let users build semantic templates. From 4.0.0 until 4.7.10, Handlebars.compile() and Handlebars.precompile() accept pre-parsed AST objects while validating only selected PathExpression, NumberLiteral, and BooleanLiteral values. This issue bypasses the AST validation introduced in version 4.7.9 for CVE-2026-33937. An attacker who can supply an object instead of a template string can place JavaScript expressions in unchecked values such as Program.blockParams.length, a non-PathExpression parameter depth, a non-string StringLiteral.value, or a non-string PathExpression.original. The compiler emits those values into generated JavaScript, causing code execution in the server process when compile output renders or wherever precompile output is loaded. Applications that pass only template strings are not affected. This issue is fixed in version 4.7.10.

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-10-06

Last Modified

2026-10-07

Generated

2026-10-19

AI Q&A

2026-10-07

EPSS Evaluated

2026-10-18

NVD

CVE-2026-106446

EUVD

EUVD-2026-93969

Affected Vendors & Products

Vendor	Product	Version / Range
handlebars-lang	handlebars.js	>= 4.0.0, < 4.7.10

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-843	The product allocates or initializes a resource such as a pointer, object, or variable using one type, but it later accesses that resource using a type that is incompatible with the original type.
CWE-94	The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.

Attack-Flow Graph

Executive Summary

This vulnerability affects Handlebars versions 4.0.0 to 4.7.9. It allows attackers to bypass AST validation by supplying pre-parsed objects instead of template strings. This can lead to JavaScript code execution on the server when the compromised templates are rendered or precompiled.

Detection Guidance

This vulnerability affects Handlebars versions 4.0.0 to 4.7.9. To detect it, check the installed version of Handlebars using: npm list handlebars. If the version is between 4.0.0 and 4.7.9, the system is vulnerable.

Impact Analysis

If you use Handlebars versions 4.0.0 to 4.7.9, an attacker could exploit this to execute arbitrary JavaScript code on your server. This could lead to data theft, unauthorized access, or system compromise depending on the application's context.

Compliance Impact

This vulnerability could lead to unauthorized code execution, potentially causing data breaches. Such breaches may violate GDPR (data protection) or HIPAA (health data security) requirements, leading to legal penalties, reputational damage, and loss of trust.

Mitigation Strategies

Update Handlebars to version 4.7.10 or later to address the vulnerability. Ensure all applications using Handlebars only pass template strings and not pre-parsed AST objects.

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