PT-2026-28571 · Unknown+1 · Handlebars+1

Trace37Labs

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Published

2026-03-27

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Updated

2026-04-10

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CVE-2026-33939

CVSS v3.1

7.5

High

VectorAV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Name of the Vulnerable Software and Affected Versions Handlebars versions 4.0.0 through 4.7.8
Description Handlebars templates containing decorator syntax referencing an unregistered decorator (e.g., {{*n}}) can cause a Denial of Service. The compiled template calls lookupProperty(decorators, "n"), which returns undefined. The runtime then attempts to invoke this undefined value as a function, resulting in an unhandled TypeError: ... is not a function that crashes the Node.js process. Applications compiling user-supplied templates without error handling are susceptible to a single-request Denial of Service. The lookupProperty() function is involved in the process. An attacker can submit a malicious template like {{*n}} to an endpoint that calls Handlebars.compile(userInput)(), causing the server process to crash repeatedly if a process manager restarts it automatically.
Recommendations Versions prior to 4.7.9 are affected. Wrap compilation and rendering in try/catch blocks. Validate template input before compilation and reject templates containing decorator syntax ({{*...}}) if decorators are not used. Use the pre-compilation workflow by compiling templates at build time and serving only pre-compiled templates; avoid calling compile() at request time.

Exploit

Fix

Improper Check for Exceptional Conditions

Weakness Enumeration

CWE-754

Related Identifiers

CVE-2026-33939
GHSA-9CX6-37PM-9JFF

Affected Products

Handlebars
Node.Js