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CVE-2026-33937

Handlebarsjs Handlebars remote code execution

9.8 CRITICALPublic exploitEPSS 1.74%
  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, `Handlebars.compile()` accepts a pre-parsed AST object in addition to a template string. The `value` field of a `NumberLiteral` AST node is emitted directly into the generated JavaScript without quoting or sanitization. An attacker who can supply a crafted AST to `compile()` can therefore inject and execute arbitrary JavaScript, leading to Remote Code Execution on the server. Version 4.7.9 fixes the issue. Some workarounds are available. Validate input type before calling `Handlebars.compile()`; ensure the argument is always a `string`, never a plain object or JSON-deserialized value. Use the Handlebars runtime-only build (`handlebars/runtime`) on the server if templates are pre-compiled at build time; `compile()` will be unavailable.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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-2026-33937 being actively exploited?

CVE-2026-33937 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 1.74%.

How severe is CVE-2026-33937?

CVE-2026-33937 has a CVSS 3.1 base score of 9.8, rated critical. EPSS estimates a 1.74% probability of exploitation.

Which products are affected by CVE-2026-33937?

Affected products include Handlebarsjs Handlebars.

How do I fix CVE-2026-33937?

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-2026-33937 against the real software inventory on every managed device, every day. 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.