GitHub Advisoryadvisory · npm

GHSA-4q55-j62x-fr9h devalue: Malformed null-prototype object keys bypass __proto__ rejection via property-key coercion

MEDIUM Published 2026-10-01 Modified 2026-10-01 Official page ↗
Ecosystem
npm
Packages
devalue
Severity
Moderate
CVSS vector
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
Weaknesses
CWE-1321
Reviewed
2026-10-01

Affected packages

• npm devalue: < 5.9.3 → fixed in 5.9.3

Description

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.

Related

Weakness · CWE (1)

  • CWE-1321 Improperly Controlled Modification of Object Prototype Attributes weakness

References