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CVE-2019-19919 — Prototype Pollution in handlebars — CVE Details

CRITICAL

Prototype Pollution in handlebars

Published December 26, 2019Updated September 10, 2026Source: osv

Summary

Versions of `handlebars` prior to 3.0.8 or 4.3.0 are vulnerable to Prototype Pollution leading to Remote Code Execution. Templates may alter an Objects' `__proto__` and `__defineGetter__` properties, which may allow an attacker to execute arbitrary code through crafted payloads. ## Recommendation Upgrade to version 3.0.8, 4.3.0 or later.

Advisory Timeline

  • First published December 26, 2019 (2482 days ago).
  • Last revised September 10, 2026 — 2449 days after initial publication.

Remediation

Upgrade to the fixed version using your package manager.

npm
Update handlebars to 4.3.0 or later
npm install handlebars@4.3.0
npm
Update handlebars to 3.0.8 or later
npm install handlebars@3.0.8

After upgrading, run your dependency scanner again to confirm the vulnerability is resolved.

Affected Packages (3)

Affects 2 ecosystems: npm (1), rubygems (1).

PackageEcosystemAffectedFixed In
handlebars
npm
All versions4.3.0
handlebars
npm
All versions3.0.8
bootstrap-wysihtml5-rails
rubygems
0.3.3.5, 0.3.3.6, 0.3.3.7, 0.3.3.8Range-based data available

Vulnerability Classification

Common Weakness Enumeration (CWE) identifiers for this vulnerability type.

CVSS Score Breakdown

What the CVSS (Common Vulnerability Scoring System) 9.8 score means for each attack dimension.

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References

Frequently Asked Questions

What is CVE-2019-19919?
Prototype Pollution in handlebars This vulnerability has been assigned a severity rating of CRITICAL (CVSS score: 9.8/10).
How do I check if my project is affected by CVE-2019-19919?
CVE-2019-19919 affects handlebars and bootstrap-wysihtml5-rails. Use GeekWala's free vulnerability scanner to check your dependencies against CVE-2019-19919 and 200,000+ other known vulnerabilities.

Severity & Exploitability

CVSS Score
9.8

Exploitation is straightforward and causes maximum impact. Patch immediately.

Also Known As

GHSA-w457-6q6x-cgp9

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