Access of Resource Using Incompatible Type ('Type Confusion') Affecting handlebars package, versions >=4.0.0 <4.7.9
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Start learning- Snyk IDSNYK-JS-HANDLEBARS-15803084
- published29 Mar 2026
- disclosed27 Mar 2026
- creditRealHurrison
Introduced: 27 Mar 2026
NewCVE-2026-33937 (opens in a new tab)How to fix?
Upgrade handlebars to version 4.7.9 or higher.
Overview
handlebars is an extension to the Mustache templating language.
Affected versions of this package are vulnerable to Access of Resource Using Incompatible Type ('Type Confusion') via the compile function. An attacker can execute arbitrary code by supplying a crafted Abstract Syntax Tree (AST) object with a malicious NumberLiteral value, which is emitted directly into generated JavaScript code without proper sanitization.
Note: This allows the attacker to inject and run arbitrary commands on the server. This is only exploitable if user-controlled JSON is deserialized and passed directly to the compile function.
Workaround
This vulnerability can be mitigated by validating that the input to the compile function is always a string and not a plain object or JSON-deserialized value, or by using the runtime-only build where compile is unavailable.