Is CVE-2026-33940 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-33940 being exploited in the wild.

How severe is CVE-2026-33940?

High severity, with a CVSS score of 8.1, published 27 March 2026.

Which products and versions are affected?

handlebars (npm) SEMVER:introduced=4.0.0,fixed=4.7.9.

Is there a fix for CVE-2026-33940?

Yes. handlebars (npm): upgrade to 4.7.9 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-33940 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-33940?

Check whether you run handlebars (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-33940: Handlebars.js remote code execution via AST type confusion

CVE-2026-33940 · Severity: high · CVSS 8.1 · Published 2026-03-27

Handlebars is a popular library used to generate web pages and other documents from templates. A security flaw in certain versions allows an attacker to inject malicious code into the server's memory by providing a specially crafted data object. If successful, this could allow the attacker to take full control of the server, steal sensitive data, or disrupt operations.

Technologies: handlebars (npm). Vendors: npm.

Quick answers

Is CVE-2026-33940 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-33940 being exploited in the wild.
How severe is CVE-2026-33940?: High severity, with a CVSS score of 8.1, published 27 March 2026.
Which products and versions are affected?: handlebars (npm) SEMVER:introduced=4.0.0,fixed=4.7.9.
Is there a fix for CVE-2026-33940?: Yes. handlebars (npm): upgrade to 4.7.9 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-33940 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-33940?: Check whether you run handlebars (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

handlebars (npm): upgrade to 4.7.9 or later
```
npm install handlebars@4.7.9
```

Technical details

A type confusion vulnerability exists in the Handlebars runtime within the `resolvePartial()` and `invokePartial()` functions. By providing a crafted object with a `call: true` property in the template context, an attacker can bypass conditional guards in `resolvePartial()`, causing `invokePartial()` to return `undefined`. The runtime then incorrectly treats this object as an uncompiled partial and passes it to `env.compile()`. Since the crafted object is a valid Handlebars AST containing injected code, the resulting JavaScript executes arbitrary commands on the server. This exploit requires the attacker to control a value used in a dynamic partial lookup (e.g., `{{> (lookup ...)}}`). The issue is fixed in version 4.7.9.

Affected products

handlebars-lang handlebars.js >= 4.0.0, <= 4.7.8

Identifiers

CVE-2026-33940
GHSA-xhpv-hc6g-r9c6

Timeline

2026-03-24: other: Fix authored
2026-03-26: patched: Version 4.7.9 released
2026-03-27: disclosed: CVE published

References

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