# CVE-2026-33938: Handlebars.js has JavaScript Injection via AST Type Confusion by tampering @partial-block

> CVE-2026-33938: Handlebars.js has JavaScript Injection via AST Type Confusion by tampering @partial-block. CVSS 8.1 (CVSS 3.1), named in 1 status incident(s).

Canonical: https://rewindex.com/cve/CVE-2026-33938
Last updated: 2026-09-04T13:19:25Z

- Published: 2026-03-27 21:05 UTC · Updated: 2026-09-04 13:19 UTC · Assigner: GitHub\_M
- CVSS: 8.1 (CVSS 3.1) · Severity: High · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
- EPSS: n/a
- CISA KEV: no
- CWE: CWE-843, CWE-94

## Description

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 vendors and products

- handlebars-lang: handlebars.js
- Red Hat: Cluster Observability Operator 1.5.0
- Red Hat: Cryostat 4
- Red Hat: Logging Subsystem for Red Hat OpenShift
- Red Hat: Red Hat Data Grid 8
- Red Hat: Red Hat Developer Hub
- Red Hat: Red Hat Enterprise Linux 10
- Red Hat: Red Hat Enterprise Linux 7
- Red Hat: Red Hat Enterprise Linux 8
- Red Hat: Red Hat Enterprise Linux 9
- Red Hat: Red Hat OpenShift AI (RHOAI)
- Red Hat: Red Hat OpenShift Dev Spaces
- Red Hat: Red Hat OpenShift Dev Spaces 3.27
- Red Hat: Red Hat Process Automation 7

## Status incidents that name it

- 2026-04-03 15:32 UTC [Wiz: Some customers may see critical issues created from incorrectly classified vulnerability findings for CVE-2026-4800, CVE-2026-33937, CVE-2026-33938, and CVE-2026-33940](https://rewindex.com/company/wiz/incidents/p2c1vhj4cq2k.md) (names this CVE): “…may see critical issues created from incorrectly classified vulnerability findings for CVE-2026-4800, CVE-2026-33937, CVE-2026-33938, and CVE-2026-33940 This incident has been resolved. This incident has been resolved. A fix has been implemented and…”

## References

- [CVE record on cve.org](https://www.cve.org/CVERecord?id=CVE-2026-33938)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-33938)
- [https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2](https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2)
- [https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9](https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9)
- [https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-3mfm-83xf-c92r](https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-3mfm-83xf-c92r)

---

_Sources: CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (https://www.cve.org/) This product uses data from the NVD API but is not endorsed or certified by the NVD. (https://nvd.nist.gov/) Known Exploited Vulnerabilities catalog from CISA. (https://www.cisa.gov/known-exploited-vulnerabilities-catalog) EPSS scores from FIRST (Exploit Prediction Scoring System). (https://www.first.org/epss/)_


---
Canonical: https://rewindex.com/cve/CVE-2026-33938 · Markdown: https://rewindex.com/cve/CVE-2026-33938.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-33938 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T02:16:34.659Z