CVE-2021-23594: Realms shim Prototype Pollution Vulnerability

CRITICAL
Advisory Identifier: GHSA-pwm7-qr6j-3vjg
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CVSS 9.8
CWE-1321
Published
Advisory Summary

CVE-2021-23594 is a CRITICAL (CVSS 9.8) prototype pollution vulnerability (CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')) affecting Realms shim libraries in the npm ecosystem. The issue involves prototype pollution in realms-shim. Remediation is available in the latest vendor maintenance releases.

CVE-2021-23594 at a Glance

CVE Identifier CVE-2021-23594
GHSA Identifier GHSA-pwm7-qr6j-3vjg
Severity CRITICAL
CVSS v3.1 Base Score 9.8
CWE Classification CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
Affected Product Realms shim
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-2021-23594

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

realms-shim fixed: Latest secure release 
npm install realms-shim@Latest secure release
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 realms-shim

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2021-23594, inspect your project dependencies using npm:

npm ls realms-shim

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

Note: The npm ls realms-shim 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-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution'), where the product receives input from an upstream component that specifies attributes that are to be initialized or updated in an object, but it does not properly control modifications of attributes of the object prototype. In Realms shim, 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

All versions of package realms-shim are vulnerable to Sandbox Bypass via a Prototype Pollution attack vector.

CVE-2021-23594 Affected Realms shim Versions

1 component(s)
Product / Package Ecosystem Affected Versions Fixed Version
realms-shim
npm/realms-shim
npm
≤ 1.2.2

References

NVD — CVE-2021-23594 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-23594
Realms shim Source Repository REPOSITORY
https://github.com/Agoric/realms-shim
snyk.io/vuln/snyk-js-realms... WEB
https://snyk.io/vuln/SNYK-JS-REALMSSHIM-2309907
www.npmjs.com/package/realms-shim WEB
https://www.npmjs.com/package/realms-shim

Frequently Asked Questions

What is CVE-2021-23594?
CVE-2021-23594 is a security vulnerability in Realms shim involving Prototype Pollution in realms-shim under CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution').
Which Realms shim versions are affected?
Affected versions include releases prior to current release patches across affected packages: realms-shim.
What version fixes CVE-2021-23594?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
Is realms-shim affected?
Yes, realms-shim is affected in releases prior to Latest secure release. Upgrade your dependency to Latest secure release or later.
What is the CVSS score of CVE-2021-23594?
CVE-2021-23594 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-2021-23594?
CVE-2021-23594 is classified under CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') (The product receives input from an upstream component that specifies attributes that are to be initialized or updated in an object, but it does not properly control modifications of attributes of the object prototype.).
How can I check npm dependencies for CVE-2021-23594?
Run the dependency tree command: 'npm ls realms-shim'. 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-pwm7-qr6j-3vjg",
  "modified" : "2022-01-11T18:14:15Z",
  "published" : "2022-01-12T22:56:13Z",
  "aliases" : [ "CVE-2021-23594" ],
  "summary" : "Prototype Pollution in realms-shim",
  "details" : "All versions of package realms-shim are vulnerable to Sandbox Bypass via a Prototype Pollution attack vector.",
  "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" : "realms-shim"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "1.2.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-23594"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/Agoric/realms-shim"
  }, {
    "type" : "WEB",
    "url" : "https://snyk.io/vuln/SNYK-JS-REALMSSHIM-2309907"
  }, {
    "type" : "WEB",
    "url" : "https://www.npmjs.com/package/realms-shim"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1321" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2022-01-11T18:14:15Z",
    "nvd_published_at" : "2022-01-10T14:10:00Z"
  }
}