GHSA-4q55-j62x-fr9h: devalue Malformed Null-prototype Object Keys Bypass Vulnerability

MODERATE
Share
CWE-1321
Published
Advisory Summary

GHSA-4q55-j62x-fr9h is a MODERATE malformed null-prototype object keys bypass vulnerability (CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')) affecting devalue libraries in the npm ecosystem. The issue involves malformed null-prototype object keys bypass __proto__ rejection via property-key coercion. Remediation is available by upgrading affected packages to version 5.9.3.

GHSA-4q55-j62x-fr9h at a Glance

CVE Identifier N/A
GHSA Identifier GHSA-4q55-j62x-fr9h
Severity MODERATE
CVSS v3.1 Base Score N/A
CWE Classification CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
Affected Product devalue
Package Ecosystem npm
Published Date
Last Updated

How to Fix GHSA-4q55-j62x-fr9h

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

devalue fixed: 5.9.3 
npm install devalue@5.9.3
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 devalue

How to Check if You Are Affected

To determine whether your Node.js application is affected by GHSA-4q55-j62x-fr9h, inspect your project dependencies using npm:

npm ls devalue

Analyze the terminal output to locate any version of devalue in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 5.9.3), your application is affected.

Note: The npm ls devalue 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 devalue, 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

This is another instance of https://github.com/sveltejs/devalue/security/advisories/GHSA-mwv9-gp5h-frr4, where some payloads could cause `parse` to create objects with a `__proto__` own property. This on its own is not enough to cause prototype pollution, and indeed this is actually how `JSON.parse` works, but we decided to be a little more defensive here and not allow the creation of objects with `__proto__` own-properties. It is very unlikely for this to cause any issues.

GHSA-4q55-j62x-fr9h Affected devalue Versions

1 component(s)
Fixed Versions:
5.9.3
Product / Package Ecosystem Affected Versions Fixed Version
devalue
npm/devalue
npm
< 5.9.3
5.9.3

References

GitHub Advisory / Wiki ADVISORY
https://github.com/sveltejs/devalue/security/advisories/GHSA-4q55-j62x-fr9h
Security Fix Commit FIX COMMIT
https://github.com/sveltejs/devalue/commit/9ec513072e31f45e60d44dad6f0dba9c92bb8675
devalue Source Repository REPOSITORY
https://github.com/sveltejs/devalue
devalue Release RELEASE
https://github.com/sveltejs/devalue/releases/tag/v5.9.3

Frequently Asked Questions

What is GHSA-4q55-j62x-fr9h?
GHSA-4q55-j62x-fr9h is a security vulnerability in devalue involving Malformed null-prototype object keys bypass __proto__ rejection via property-key coercion under CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution').
Which devalue versions are affected?
Affected versions include releases prior to 5.9.3 across affected packages: devalue.
What version fixes GHSA-4q55-j62x-fr9h?
Upgrading to 5.9.3 (or the latest patched release for your respective branch) resolves the vulnerability.
Is devalue affected?
Yes, devalue is affected in releases prior to 5.9.3. Upgrade your dependency to 5.9.3 or later.
What CWE is associated with GHSA-4q55-j62x-fr9h?
GHSA-4q55-j62x-fr9h 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 GHSA-4q55-j62x-fr9h?
Run the dependency tree command: 'npm ls devalue'. 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-4q55-j62x-fr9h",
  "modified" : "2026-10-01T15:13:23Z",
  "published" : "2026-10-01T15:13:23Z",
  "aliases" : [ ],
  "summary" : "devalue: Malformed null-prototype object keys bypass __proto__ rejection via property-key coercion",
  "details" : "This is another instance of https://github.com/sveltejs/devalue/security/advisories/GHSA-mwv9-gp5h-frr4, where some payloads could cause `parse` to create objects with a `__proto__` own property. This on its own is not enough to cause prototype pollution, and indeed this is actually how `JSON.parse` works, but we decided to be a little more defensive here and not allow the creation of objects with `__proto__` own-properties. It is very unlikely for this to cause any issues.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "devalue"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "5.9.3"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 5.9.2"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/sveltejs/devalue/security/advisories/GHSA-4q55-j62x-fr9h"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/sveltejs/devalue/commit/9ec513072e31f45e60d44dad6f0dba9c92bb8675"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/sveltejs/devalue"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/sveltejs/devalue/releases/tag/v5.9.3"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1321" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-10-01T15:13:23Z",
    "nvd_published_at" : null
  }
}