CVE-2026-106446
Received
Received - Intake
Handlebars Template Engine Code Execution via AST Injection
Vulnerability report for CVE-2026-106446, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-10-06
Last updated on: 2026-10-06
Assigner: GitHub, Inc.
Description
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
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| Percentile: |
Meta Information
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. |
