CVE-2026-106446

Published Oct 6, 2026

Last updated 33 minutes ago

Overview

AI description

Automated description summarized from trusted sources.

CVE-2026-106446 is an Abstract Syntax Tree (AST) type confusion vulnerability affecting the JavaScript templating library Handlebars.js in versions 4.0.0 through 4.7.9. The flaw resides in the `compile()` and `precompile()` functions, which accept pre-parsed AST objects but only validate specific nodes, such as selected PathExpression, NumberLiteral, and BooleanLiteral values. This incomplete validation allows an attacker who can supply an object instead of a standard template string to bypass previous security controls (specifically the fix for CVE-2026-33937) and inject arbitrary JavaScript expressions into unchecked fields, such as `Program.blockParams.length` or non-string values. When the compiler processes these unchecked values, it emits them directly into the generated JavaScript code. This leads to arbitrary code execution within the server process when the compiled output is rendered or when precompiled output is loaded. Applications that only pass trusted template strings to the compiler are not affected by this issue. The vulnerability has been resolved in Handlebars.js version 4.7.10.

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.
Source: security-advisories@github.com
NVD status: Awaiting Analysis

Risk scores

CVSS 3.1

Type: Secondary
Base score: 9.8
Impact score: 5.9
Exploitability score: 3.9
Vector string: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Severity: CRITICAL

Weaknesses

security-advisories@github.com: CWE-94

Hype score: Not currently trending

References