CVE-2019-20920: Handlebars Arbitrary Code Execution Vulnerability

HIGH
Advisory Identifier: GHSA-3cqr-58rm-57f8
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CVSS 8.1
CWE-94
Published
Advisory Summary

CVE-2019-20920 is a HIGH (CVSS 8.1) arbitrary code execution vulnerability (CWE-94: Improper Control of Generation of Code ('Code Injection')) affecting Handlebars libraries in the npm ecosystem. The issue involves arbitrary code execution in handlebars. Remediation is available by upgrading affected packages to version 3.0.8, 4.5.3.

CVE-2019-20920 at a Glance

CVE Identifier CVE-2019-20920
GHSA Identifier GHSA-3cqr-58rm-57f8
Severity HIGH
CVSS v3.1 Base Score 8.1
CWE Classification CWE-94: Improper Control of Generation of Code ('Code Injection')
Affected Product Handlebars
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 8.1

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:L/A:L).

Attack Vector Network (AV:N)
Attack Complexity High (AC:H)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Changed (S:C)
Confidentiality High (C:H)
Integrity Low (I:L)
Availability Low (A:L)

How to Fix CVE-2019-20920

To remediate this vulnerability, upgrade all affected Handlebars dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

handlebars fixed: 3.0.8 
npm install handlebars@3.0.8
handlebars fixed: 4.5.3 
npm install handlebars@4.5.3
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls handlebars

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2019-20920, inspect your project dependencies using npm:

npm ls handlebars

Analyze the terminal output to locate any version of Handlebars in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 3.0.8), your application is affected.

Note: The npm ls handlebars command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-94: Improper Control of Generation of Code ('Code Injection'), where 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. In Handlebars, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

Handlebars before 3.0.8 and 4.x before 4.5.3 is vulnerable to Arbitrary Code Execution. The lookup helper fails to properly validate templates, allowing attackers to submit templates that execute arbitrary JavaScript. This can be used to run arbitrary code on a server processing Handlebars templates or in a victim's browser (effectively serving as XSS).

CVE-2019-20920 Affected Handlebars Versions

2 component(s)
Fixed Versions:
3.0.84.5.3
Product / Package Ecosystem Affected Versions Fixed Version
handlebars
npm/handlebars
npm
< 3.0.8
3.0.8
handlebars
npm/handlebars
npm
≥ 4.0.0
< 4.5.3
4.5.3

References

NVD — CVE-2019-20920 NVD
https://nvd.nist.gov/vuln/detail/CVE-2019-20920
Security Fix Commit FIX COMMIT
https://github.com/handlebars-lang/handlebars.js/commit/156061eb7707575293613d7fdf90e2bdaac029ee
Security Fix Commit FIX COMMIT
https://github.com/handlebars-lang/handlebars.js/commit/d54137810a49939fd2ad01a91a34e182ece4528e
snyk.io/vuln/snyk-js-handle... WEB
https://snyk.io/vuln/SNYK-JS-HANDLEBARS-534478
www.npmjs.com/advisories/1316 WEB
https://www.npmjs.com/advisories/1316
www.npmjs.com/advisories/1324 WEB
https://www.npmjs.com/advisories/1324
www.npmjs.com/package/handlebars WEB
https://www.npmjs.com/package/handlebars

Frequently Asked Questions

What is CVE-2019-20920?
CVE-2019-20920 is a security vulnerability in Handlebars involving Arbitrary Code Execution in Handlebars under CWE-94: Improper Control of Generation of Code ('Code Injection').
Which Handlebars versions are affected?
Affected versions include releases prior to 3.0.8, 4.5.3 across affected packages: handlebars.
What version fixes CVE-2019-20920?
Upgrading to 3.0.8, 4.5.3 (or the latest patched release for your respective branch) resolves the vulnerability.
Is handlebars affected?
Yes, handlebars is affected in releases prior to 3.0.8, 4.5.3. Upgrade your dependency to 3.0.8, 4.5.3 or later.
What is the CVSS score of CVE-2019-20920?
CVE-2019-20920 has a CVSS v3.1 base score of 8.1 (HIGH) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:L/A:L.
What CWE is associated with CVE-2019-20920?
CVE-2019-20920 is classified under CWE-94: Improper Control of Generation of Code ('Code Injection') (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.).
How can I check npm dependencies for CVE-2019-20920?
Run the dependency tree command: 'npm ls handlebars'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-3cqr-58rm-57f8",
  "modified" : "2021-04-22T23:38:32Z",
  "published" : "2022-02-10T20:38:19Z",
  "aliases" : [ "CVE-2019-20920" ],
  "summary" : "Arbitrary Code Execution in Handlebars",
  "details" : "Handlebars before 3.0.8 and 4.x before 4.5.3 is vulnerable to Arbitrary Code Execution. The lookup helper fails to properly validate templates, allowing attackers to submit templates that execute arbitrary JavaScript. This can be used to run arbitrary code on a server processing Handlebars templates or in a victim's browser (effectively serving as XSS).",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:L/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "handlebars"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.0.8"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "npm",
      "name" : "handlebars"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.0.0"
      }, {
        "fixed" : "4.5.3"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2019-20920"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/handlebars-lang/handlebars.js/commit/156061eb7707575293613d7fdf90e2bdaac029ee"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/handlebars-lang/handlebars.js/commit/d54137810a49939fd2ad01a91a34e182ece4528e"
  }, {
    "type" : "WEB",
    "url" : "https://snyk.io/vuln/SNYK-JS-HANDLEBARS-534478"
  }, {
    "type" : "WEB",
    "url" : "https://www.npmjs.com/advisories/1316"
  }, {
    "type" : "WEB",
    "url" : "https://www.npmjs.com/advisories/1324"
  }, {
    "type" : "WEB",
    "url" : "https://www.npmjs.com/package/handlebars"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-94" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-04-22T23:38:32Z",
    "nvd_published_at" : "2020-09-30T18:15:00Z"
  }
}