---
title: "CVE-2026-106445: Handlebars: JavaScript Injection via Own Property Check Bypass"
url: https://erroneo.us/security/cve/CVE-2026-106445/
description: "CVE-2026-106445 (handlebars (npm)): Handlebars provides the power necessary to let users build semantic templates. From 3.0.0 until 4.7.10, Handlebars…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-10-06
date_modified: 2026-10-12
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-106445"
kev: false
cvss: 9.2
epss: 0.00411
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-106445: Handlebars: JavaScript Injection via Own Property Check Bypass

**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 0.4% , percentile 34: FIRST’s model estimates a 0.4% chance of exploitation activity in the next 30 days, higher than 34% 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) >= 3.0.0, <= 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 3.0.0 until 4.7.10, Handlebars lookupProperty returns Function.prototype.constructor before applying the prototype-access deny list because constructor is an own property of Function.prototype. When an attacker can render a controlled template with allowProtoMethodsByDefault enabled and an accessible function in the template context, the template can traverse from that function through its prototype to Function.prototype and then obtain the Function constructor through the own-property bypass. This permits attacker-controlled JavaScript to execute with the server application's privileges. This issue is fixed in version 4.7.10.

## Affected packages

- npm `handlebars` >= 3.0.0, <= 4.7.9 → fixed: 4.7.10

## Affected products (CVE record)

- handlebars-lang handlebars.js: >= 3.0.0, < 4.7.10

## Severity

- GitHub_M CVSS 4.0: 9.2 `CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`
- GitHub CVSS 4.0: 9.2 `CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`

## 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): 0.41% probability of exploitation activity in the next 30 days; percentile 34.

## Sources

- [GitHub Advisory GHSA-p8wg-vrv2-v86f](https://github.com/advisories/GHSA-p8wg-vrv2-v86f)
- [CVE.org record CVE-2026-106445](https://www.cve.org/CVERecord?id=CVE-2026-106445)
- [NVD entry CVE-2026-106445](https://nvd.nist.gov/vuln/detail/CVE-2026-106445)
- [github.com](https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-p8wg-vrv2-v86f)
- [github.com](https://github.com/handlebars-lang/handlebars.js/pull/2185)
- [github.com](https://github.com/handlebars-lang/handlebars.js/commit/ceec388abe1d1aac8f6369860d5f390fa71ef4fa)
- [github.com](https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.10)

---
Source page: https://erroneo.us/security/cve/CVE-2026-106445/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt