---
title: "CVE-2026-106446: Handlebars: JavaScript Injection via AST Type Confusion in compile (bypass of CVE-2026-33937)"
url: https://erroneo.us/security/cve/CVE-2026-106446/
description: "CVE-2026-106446 (handlebars (npm)): Handlebars provides the power necessary to let users build semantic templates. From 4.0.0 until 4.7.10…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-10-06
date_modified: 2026-10-08
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-106446"
kev: false
cvss: 9.8
epss: 0.0064
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-106446: Handlebars: JavaScript Injection via AST Type Confusion in compile (bypass of CVE-2026-33937)

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Not in CISA KEV , but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 0.6% , percentile 50: FIRST’s model estimates a 0.6% chance of exploitation activity in the next 30 days, higher than 50% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes handlebars (npm) >= 4.0.0, <= 4.7.9, fixed in 4.7.10 . Check your lockfile, including transitive dependencies.

## What it is

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.

## Affected packages

- npm `handlebars` >= 4.0.0, <= 4.7.9 → fixed: 4.7.10

## Affected products (CVE record)

- handlebars-lang handlebars.js: >= 4.0.0, < 4.7.10

## Severity

- GitHub_M CVSS 3.1: 9.8 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`
- GitHub CVSS 3.1: 9.8 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 0.64% probability of exploitation activity in the next 30 days; percentile 50.

## Sources

- [GitHub Advisory GHSA-8r5x-fm3f-whwj](https://github.com/advisories/GHSA-8r5x-fm3f-whwj)
- [CVE.org record CVE-2026-106446](https://www.cve.org/CVERecord?id=CVE-2026-106446)
- [NVD entry CVE-2026-106446](https://nvd.nist.gov/vuln/detail/CVE-2026-106446)
- [github.com](https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-8r5x-fm3f-whwj)
- [github.com](https://github.com/handlebars-lang/handlebars.js/pull/2185)
- [github.com](https://github.com/handlebars-lang/handlebars.js/commit/703fdcc5fd6cc8d1cc0c33cc19de40c467c4b8d2)
- [github.com](https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.10)

---
Source page: https://erroneo.us/security/cve/CVE-2026-106446/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt