CVE-2026-33940

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.

Overview

State: PUBLISHED
Assigner (CNA): GitHub_M
CVSS severity: HIGH
CVSS score: 8.1 / 10
CVSS vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Effective score: 8.1 / 10 HIGH source: CNA overview
MSRC score: 8.1 / 10 HIGH MS rating: Important
CWE(s): CWE-94, CWE-843
Reserved: 2026-03-24
Published: 2026-03-27 22:11 UTC
Last updated: 2026-04-01 05:55 UTC
Source: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/33xxx/CVE-2026-33940.json
Linked Threat: CVE-2026-33940 — Handlebars.js has JavaScript Injection via AST Type Confusion when passing an object as dynamic partial

NVD triage scoring NVD CVE 2.0

Layer NVD adds on top of the CNA's CVE record — published / last-modified timestamps, exploitability / impact subscores, and the FIRST.org EPSS probability that this CVE will be exploited in the wild in the next 30 days.

NVD published: 2026-03-27 22:16:21 UTC
NVD last modified: 2026-03-31 17:51:04 UTC
NVD CVSS v3.1: 8.1 / 10 HIGH source: security-advisories@github.com
NVD CVSS vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Exploitability subscore: 2.2 / 10
Impact subscore: 5.9 / 10
EPSS score: 0.0003 (probability of exploitation in next 30 days)
EPSS percentile: 9.17% vs all CVEs — higher = more likely to be exploited, as of 2026-05-24

European Union Vulnerability Database ENISA EUVD

ENISA's official EU repository for curated vulnerability intelligence. Carries a separate identifier (EUVD-YYYY-NNNN) and frequently exposes an earlier-published description + CVSS than NVD does.

EUVD ID: EUVD-2026-16860
Assigner: GitHub_M
Published: Mar 27, 2026, 9:11:10 PM
Updated: Apr 1, 2026, 3:55:41 AM
EUVD base score (CVSS 3.1): 8.1 / 10
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
EUVD-reported EPSS: 0.0300
Vendors: handlebars-lang
Products: handlebars.js (4.0.0, < 4.7.9)
Aliases: GHSA-xhpv-hc6g-r9c6

ENISA 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.

EUVD references (3)

Microsoft Security Response Center MSRC

Microsoft's vendor-authoritative record from the Security Update Guide — its own CVSS score, impact, severity rating, exploit assessment, and KB-article fixes. Refreshed 2026-08-12 01:05 UTC (source: CVRF).

MS severity: Important
MS CVSS base score: 8.1 / 10 (temporal 8.1)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Release: 2026-Mar

Affected products (1)

Vendor	Product	Versions	Platforms
handlebars-lang	handlebars.js	`>= 4.0.0, < 4.7.9` (affected)	—

Affected products — CPE 2.3 (1) NVD

NVD's normalized CPE 2.3 matchers, used by vendor tools (vulnerability scanners, asset managers) for automated detection. Compare with the CNA's free-text "Affected products" section above.

cpe:2.3:a:handlebarsjs:handlebars:*:*:*:*:*:node.js:*:*

Vendor references (3)

References embedded in the original CVE record by the assigning CNA.

https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-xhpv-hc6g-r9c6 x_refsource_CONFIRM
https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2 x_refsource_MISC
https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9 x_refsource_MISC

MITRE references (3) cveawg.mitre.org

Pulled from MITRE's CVE Services API by the 🛰 Backfill from MITRE button.

https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2 x_refsource_MISC
https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9 x_refsource_MISC
https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-xhpv-hc6g-r9c6 x_refsource_CONFIRM

Web references (1)

DuckDuckGo results ranked by threat-intel / vendor advisory domains. Generated by the 🔎 Find references (web) button above — same flow as the Remediations search.

MSRC update guide: CVE-2026-33940 msrc

NVD-tagged references (3)

Reference list NVD curates from the CNA record, vendor advisories, and third-party reports. The tag chips below are NVD's analyst-assigned categories.

https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2 security-advisories@github.com Patch
https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9 security-advisories@github.com Release Notes
https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-xhpv-hc6g-r9c6 security-advisories@github.com ExploitVendor Advisory

Indicators (2)

IOCs linked to the auto-promoted Threat row.

Type	Value	VirusTotal	Attached
domain	`handlebars.js`	no local data	2026-05-18 21:18 UTC
domain	`env.compile`	no local data	2026-05-18 21:18 UTC

Remediations (11)

Remediations are stored against the linked Threat row; the list below is deduplicated across both pages.

Oracle Critical Patch Update Advisory - April 2026

web:www.oracle.com

This Critical Patch Update contains 481 new security patches across the product families listed below. Please note that an MOS note summarizing the content of this Critical Patch Update and other Oracle Software Security Assurance activities is located at April 2026 Critical Patch Update: Executive Summary and Analysis.

2026-05-22 16:53 UTC
Patch Tuesday, April 2026 Edition - Krebs on Security

web:krebsonsecurity.com

For a clickable, per- patch breakdown, check out the SANS Internet Storm Center Patch Tuesday roundup. Running into problems applying any of these updates?

2026-05-22 03:07 UTC
Nvd - Cve-2026-33940

web:nvd.nist.gov

An official website of the United States government Here's how you know

2026-05-22 03:07 UTC
Security Update Guide - Microsoft

web:portal.msrc.microsoft.com

The Security Update Guide provides information on the latest Microsoft security updates, helping users understand and address potential vulnerabilities effectively.

2026-05-22 03:07 UTC
Microsoft April 2026 Patch Tuesday fixes 167 flaws, 2 zero-days

web:www.bleepingcomputer.com

Today is Microsoft's April 2026 Patch Tuesday with security updates for 167 flaws, including 2 zero-day vulnerabilities.

2026-05-22 03:07 UTC
Critical Patches Issued for Microsoft Products, April 14, 2026

web:www.cisecurity.org

<p>Multiple vulnerabilities have been discovered in Microsoft products, the most severe of which could allow for remote code execution. Successful exploitation of the most severe of these vulnerabilities could result in an attacker gaining the same privileges as the logged-on user. Depending on the privileges associated with the user, an attacker could then install programs; view, change, or ...

2026-05-22 03:07 UTC
April 2026 Patch Tuesday: Updates and Analysis | CrowdStrike

web:www.crowdstrike.com

Microsoft's April 2026 Patch Tuesday addresses 164 CVEs , featuring 8 Critical vulnerabilities, one exploited zero-day, and one disclosed zero-day.

2026-05-22 03:07 UTC
Microsoft April 2026 Patch Tuesday fixes 167 ... - Notebookcheck

web:www.notebookcheck.net

Microsoft April 2026 Patch Tuesday fixes 167 vulnerabilities, including an actively exploited SharePoint zero-day. Windows 11 KB5083769 and KB5082052 bring new builds and RDP security.

2026-05-22 03:07 UTC
Microsoft fixes 167 security flaws in April, second biggest Patch ...

web:www.pcworld.com

This month's Patch Tuesday includes an actively exploited Office zero-day vulnerability and several critical RCE bugs in Windows and Remote Desktop.

2026-05-22 03:07 UTC
Microsoft Patch Tuesday April 2026 - 168 Vulnerabilities Fixed ...

web:cybersecuritynews.com

Microsoft has released its April 2026 Patch Tuesday security update, addressing 168 vulnerabilities across its product portfolio including one actively exploited zero-day and one publicly disclosed flaw that organizations must prioritize immediately.

2026-05-22 03:07 UTC
Microsoft Issues Massive Windows Patch for 160+ Bugs ... - TechRepublic

web:www.techrepublic.com

Microsoft's April 2026 Patch Tuesday fixes 165 vulnerabilities, including two zero-days, in one of the company's largest monthly security updates.

2026-05-22 03:07 UTC

AI Forensic Analysis

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Raw JSON

The full cvelistV5 record. Download as CVE-2026-33940.json.

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