CVE-2021-42740: Shell quote Improper Neutralization Of Special Elements Vulnerability

CRITICAL
Advisory Identifier: GHSA-g4rg-993r-mgx7
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CVSS 9.8
CWE-77
Published
Advisory Summary

CVE-2021-42740 is a CRITICAL (CVSS 9.8) improper neutralization of special elements vulnerability (CWE-77: Improper Neutralization of Special Elements used in a Command ('Command Injection')) affecting Shell quote libraries in the npm ecosystem. The issue involves improper neutralization of special elements used in a command in shell-quote. Remediation is available by upgrading affected packages to version 1.7.3.

CVE-2021-42740 at a Glance

CVE Identifier CVE-2021-42740
GHSA Identifier GHSA-g4rg-993r-mgx7
Severity CRITICAL
CVSS v3.1 Base Score 9.8
CWE Classification CWE-77: Improper Neutralization of Special Elements used in a Command ('Command Injection')
Affected Product Shell quote
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 9.8

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

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

How to Fix CVE-2021-42740

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

shell-quote fixed: 1.7.3 
npm install shell-quote@1.7.3
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 shell-quote

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2021-42740, inspect your project dependencies using npm:

npm ls shell-quote

Analyze the terminal output to locate any version of Shell quote in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.7.3), your application is affected.

Note: The npm ls shell-quote 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-77: Improper Neutralization of Special Elements used in a Command ('Command Injection'), where the product constructs all or part of a command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended command when it is sent to a downstream component. In Shell quote, 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

The shell-quote package before 1.7.3 for Node.js allows command injection. An attacker can inject unescaped shell metacharacters through a regex designed to support Windows drive letters. If the output of this package is passed to a real shell as a quoted argument to a command with `exec()`, an attacker can inject arbitrary commands. This is because the Windows drive letter regex character class is `[A-z]` instead of the correct `[A-Za-z]`. Several shell metacharacters exist in the space between capital letter Z and lower case letter a, such as the backtick character.

CVE-2021-42740 Affected Shell quote Versions

1 component(s)
Fixed Versions:
1.7.3
Product / Package Ecosystem Affected Versions Fixed Version
shell-quote
npm/shell-quote
npm
≥ 1.6.3
< 1.7.3
1.7.3

References

NVD — CVE-2021-42740 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-42740
Security Fix Commit FIX COMMIT
https://github.com/ljharb/shell-quote/commit/5799416ed454aa4ec9afafc895b4e31760ea1abe
Shell quote Source Repository REPOSITORY
https://github.com/ljharb/shell-quote
Shell quote Source Repository REPOSITORY
https://github.com/ljharb/shell-quote/blob/master/CHANGELOG.md#173
www.npmjs.com/package/shell-quote WEB
https://www.npmjs.com/package/shell-quote

Frequently Asked Questions

What is CVE-2021-42740?
CVE-2021-42740 is a security vulnerability in Shell quote involving Improper Neutralization of Special Elements used in a Command in Shell-quote under CWE-77: Improper Neutralization of Special Elements used in a Command ('Command Injection').
Which Shell quote versions are affected?
Affected versions include releases prior to 1.7.3 across affected packages: shell-quote.
What version fixes CVE-2021-42740?
Upgrading to 1.7.3 (or the latest patched release for your respective branch) resolves the vulnerability.
Is shell-quote affected?
Yes, shell-quote is affected in releases prior to 1.7.3. Upgrade your dependency to 1.7.3 or later.
What is the CVSS score of CVE-2021-42740?
CVE-2021-42740 has a CVSS v3.1 base score of 9.8 (CRITICAL) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2021-42740?
CVE-2021-42740 is classified under CWE-77: Improper Neutralization of Special Elements used in a Command ('Command Injection') (The product constructs all or part of a command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended command when it is sent to a downstream component.).
How can I check npm dependencies for CVE-2021-42740?
Run the dependency tree command: 'npm ls shell-quote'. 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-g4rg-993r-mgx7",
  "modified" : "2025-09-10T17:27:08Z",
  "published" : "2022-05-24T19:18:27Z",
  "aliases" : [ "CVE-2021-42740" ],
  "summary" : "Improper Neutralization of Special Elements used in a Command in Shell-quote",
  "details" : "The shell-quote package before 1.7.3 for Node.js allows command injection. An attacker can inject unescaped shell metacharacters through a regex designed to support Windows drive letters. If the output of this package is passed to a real shell as a quoted argument to a command with `exec()`, an attacker can inject arbitrary commands. This is because the Windows drive letter regex character class is `[A-z]` instead of the correct `[A-Za-z]`. Several shell metacharacters exist in the space between capital letter Z and lower case letter a, such as the backtick character.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "shell-quote"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.6.3"
      }, {
        "fixed" : "1.7.3"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 1.7.2"
    }
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-42740"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/ljharb/shell-quote/commit/5799416ed454aa4ec9afafc895b4e31760ea1abe"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/ljharb/shell-quote"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/ljharb/shell-quote/blob/master/CHANGELOG.md#173"
  }, {
    "type" : "WEB",
    "url" : "https://www.npmjs.com/package/shell-quote"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-77" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2022-06-21T20:08:10Z",
    "nvd_published_at" : "2021-10-21T15:15:00Z"
  }
}