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CVE-2026-33937 PUBLISHED CVSS 9.800000190734863 CRITICAL

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.

EPSS 0.25% · 48.2th percentile

Risk Scores

CVSS v3.1
9.800000190734863
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS Score
0.25%
48.2th percentile

Affected Products

VendorProductVersions
npmhandlebars4.0.0, 4.0.0, 4.0.0
handlebarsjshandlebars4.0.0
handlebars-langhandlebars.js>= 4.0.0, < 4.7.9, >= 4.0.0, < 4.7.9, >= 4.0.0, < 4.7.9

Timeline

References

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