PT-2026-28571 · Unknown+1 · Handlebars+1
CVSS v2.0
7.8
High
| Vector | AV:N/AC:L/Au:N/C:N/I:N/A:C |
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
DoS
Improper Check for Exceptional Conditions
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Related Identifiers
Affected Products
Handlebars
Node.Js