handlebars-lang Handlebars.js up to 4.7.9 lookupProperty code injection

Summaryinfo

A vulnerability, which was classified as critical, has been found in handlebars-lang Handlebars.js up to 4.7.9. Affected by this vulnerability is the function lookupProperty. Performing a manipulation results in code injection. This vulnerability was named CVE-2026-106445. The attack may be initiated remotely. There is no available exploit. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical has been found in handlebars-lang Handlebars.js up to 4.7.9. This affects the function lookupProperty. The manipulation with an unknown input leads to a code injection vulnerability. CWE is classifying the issue as CWE-94. The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

Handlebars provides the power necessary to let users build semantic templates. From 4.0.0 until 4.7.10, Handlebars lookupProperty returns Function.prototype.constructor before applying the prototype-access deny list because constructor is an own property of Function.prototype. When an attacker can render a controlled template with allowProtoMethodsByDefault enabled and an accessible function in the template context, the template can traverse from that function through its prototype to Function.prototype and then obtain the Function constructor through the own-property bypass. This permits attacker-controlled JavaScript to execute with the server application's privileges. This issue is fixed in version 4.7.10.

The advisory is shared at github.com. This vulnerability is uniquely identified as CVE-2026-106445 since 10/06/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1059 for this issue.

Upgrading to version 4.7.10 eliminates this vulnerability.

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Productinfo

Type

• JavaScript Library

Vendor

• handlebars-lang

Name

• Handlebars.js

Version

• 4.7.0
• 4.7.1
• 4.7.2
• 4.7.3
• 4.7.4
• 4.7.5
• 4.7.6
• 4.7.7
• 4.7.8
• 4.7.9

Website

• Product: https://github.com/handlebars-lang/handlebars.js/

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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