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CVE-2026-33939

Handlebarsjs Handlebars vulnerability

7.5 HIGHPublic exploitEPSS 0.76%
  1. Published27 Mar 2026

Description

Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, when a Handlebars template contains decorator syntax referencing an unregistered decorator (e.g. `{{*n}}`), the compiled template calls `lookupProperty(decorators, "n")`, which returns `undefined`. The runtime then immediately invokes the result as a function, causing an unhandled `TypeError: ... is not a function` that crashes the Node.js process. Any application that compiles user-supplied templates without wrapping the call in a `try/catch` is vulnerable to a single-request Denial of Service. Version 4.7.9 fixes the issue. Some workarounds are available. Wrap compilation and rendering in `try/catch`. Validate template input before passing it to `compile()`; reject templates containing decorator syntax (`{{*...}}`) if decorators are not used in your application. Use the pre-compilation workflow; compile templates at build time and serve only pre-compiled templates; do not call `compile()` at request time.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityNone
IntegrityNone
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

Handlebarsjs Handlebars≥ 4.0.0 < 4.7.9

Remediation

Fixed in
Handlebarsjs Handlebars≥ 4.7.9

References

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Frequently asked

Is CVE-2026-33939 being actively exploited?

CVE-2026-33939 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.76%.

How severe is CVE-2026-33939?

CVE-2026-33939 has a CVSS 3.1 base score of 7.5, rated high. EPSS estimates a 0.76% probability of exploitation.

Which products are affected by CVE-2026-33939?

Affected products include Handlebarsjs Handlebars.

How do I fix CVE-2026-33939?

Upgrade affected software to a fixed version, for example Handlebarsjs Handlebars 4.7.9 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-33939 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.