Handlebars: JavaScript Injection via AST Type Confusion in compile (Program.blockParams)

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-106446
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-06 20:17:26 UTC
Updated2026-10-06 20:17:26 UTC
DescriptionHandlebars 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.

Risk And Classification

Primary CVSS: v3.1 9.8 CRITICAL from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Problem Types: CWE-94 | CWE-843 | CWE-94 CWE-94: Improper Control of Generation of Code ('Code Injection') | CWE-843 CWE-843: Access of Resource Using Incompatible Type ('Type Confusion')

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Handlebars-lang Handlebars.js affected >= 4.0.0, < 4.7.10 Not specified

References

ReferenceSourceLinkTags
github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-8r5x-f... [email protected] github.com
github.com/handlebars-lang/handlebars.js/pull/2185 [email protected] github.com
github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.10 [email protected] github.com
github.com/handlebars-lang/handlebars.js/commit/703fdcc5fd6cc8d1cc0c33cc... [email protected] github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

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