# CVE-2026-33940: Handlebars.js has JavaScript Injection via AST Type Confusion when passing an object as dynamic partial

> CVE-2026-33940: Handlebars.js has JavaScript Injection via AST Type Confusion when passing an object as dynamic partial. CVSS 8.1 (CVSS 3.1), named in 1 status incident(s).

Canonical: https://rewindex.com/cve/CVE-2026-33940
Last updated: 2026-09-04T13:19:26Z

- Published: 2026-03-27 21:11 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, a crafted object placed in the template context can bypass all conditional guards in \`resolvePartial()\` and cause \`invokePartial()\` to return \`undefined\`. The Handlebars runtime then treats the unresolved partial as a source that needs to be compiled, passing the crafted object to \`env.compile()\`. Because the object is a valid Handlebars AST containing injected code, the generated JavaScript executes arbitrary commands on the server. The attack requires the adversary to control a value that can be returned by a dynamic partial lookup. Version 4.7.9 fixes the issue. Some workarounds are available. First, use the runtime-only build (\`require('handlebars/runtime')\`). Without \`compile()\`,  the fallback compilation path in \`invokePartial\` is unreachable. Second, sanitize context data before rendering: Ensure no value in the context is a non-primitive  object that could be passed to a dynamic partial. Third, avoid dynamic partial lookups (\`{{\> (lookup ...)}}\`) when context data is user-controlled.

## 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 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 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): “…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 we are monitoring…”

## References

- [CVE record on cve.org](https://www.cve.org/CVERecord?id=CVE-2026-33940)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-33940)
- [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-xhpv-hc6g-r9c6](https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-xhpv-hc6g-r9c6)

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_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/)_


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Canonical: https://rewindex.com/cve/CVE-2026-33940 · Markdown: https://rewindex.com/cve/CVE-2026-33940.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-33940 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T04:04:14.694Z