Critical · CVSS 9.2CVE-2026-106445

Handlebars: JavaScript Injection via Own Property Check BypassCVE-2026-106445

Answer in brief

CVE-2026-106445 records a Critical severity (CVSS 9.2) vulnerability in Handlebars: JavaScript Injection via Own Property Check Bypass. The current sources do not mark it as known exploited. The current feed maps handlebars-lang/handlebars.js (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Oct 6, 2026Updated Oct 6, 2026Source checked Oct 7, 2026First seen by HOL Oct 6, 2026Material review Oct 6, 2026

Upstream Advisory

Key facts

Risk: Critical · CVSS 9.2
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 9.2. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps handlebars-lang/handlebars.js (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
handlebars-lang/handlebars.jsgeneric	>=4.0.0 <4.7.10	4.7.10

Recommended response

Check inventory. Check lockfiles and deployed manifests for handlebars-lang/handlebars.js.
Review the reported fix. Update handlebars-lang/handlebars.js to 4.7.10 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Oct 6, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Oct 6, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Oct 6, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.