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CVE-2026-106445

CriticalCVSS 9.2 / 10
Published Oct 6, 2026·Last modified Oct 8, 2026
Affected Components(42)
handlebars-lang/handlebars.js
4.0.1
handlebars-lang/handlebars.js
4.0.12
handlebars-lang/handlebars.js
4.5.2
1 / 14
Description

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.

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Risk Scores
Base Score
9.2

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability.

Threat Intelligence
7.2

Exploitation activity has been observed. Apply available patches or mitigations urgently.

EPSS
0.41%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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