---
id: CVE-2026-33938
title: Handlebars provides the power necessary to let users build semantic templates
summary: >-
  Handlebars provides the power necessary to let users build semantic templates.
  In versions 4.0.0 through 4.7.8, the `@partial-block` special variable is
  stored in the template data context and is reachable and mutable from within a
  templ…
severity: high
cvss: 8.1
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H'
cwe:
  - CWE-94
  - CWE-843
  - CWE-917
vendor: handlebarsjs
product: handlebars
affected:
  - 'handlebars >= 4.0.0, < 4.7.9'
patched:
  - handlebars 4.7.9
published: '2026-03-27'
updated: '2026-07-02'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-33938'
references:
  - url: >-
      https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2
    label: security-advisories@github.com
  - url: 'https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9'
    label: security-advisories@github.com
  - url: >-
      https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-3mfm-83xf-c92r
    label: security-advisories@github.com
  - url: 'https://access.redhat.com/errata/RHSA-2026:10175'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/errata/RHSA-2026:34342'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/security/cve/CVE-2026-33938'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2452525'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: >-
      https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-3mfm-83xf-c92r
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33938.json
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
tags:
  - nvd
epss: 0.00843
epssPercentile: 0.5618
ingestedAt: '2026-07-02T12:34:40.406Z'
---

## Overview

Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, the `@partial-block` special variable is stored in the template data context and is reachable and mutable from within a template via helpers that accept arbitrary objects. When a helper overwrites `@partial-block` with a crafted Handlebars AST, a subsequent invocation of `{{> @partial-block}}` compiles and executes that AST, enabling arbitrary JavaScript execution on the server. Version 4.7.9 fixes the issue. Some workarounds are available. First, use the runtime-only build (`require('handlebars/runtime')`). The `compile()` method is  absent, eliminating the vulnerable fallback path. Second, audit registered helpers for any that write arbitrary values to context objects. Helpers  should treat context data as read-only. Third, avoid registering helpers from third-party packages (such as `handlebars-helpers`) in  contexts where templates or context data can be influenced by untrusted input.

## Affected

- `handlebars >= 4.0.0, < 4.7.9`

## Remediation

Upgrade past the affected range:

- `handlebars 4.7.9`