Critical

flat vulnerable to Prototype Pollution

  • Disclosed: 25.12.2022
  • Updated: 11.10.2026 10:22

flat helps flatten/unflatten nested Javascript objects. A vulnerability, which was classified as critical, was found in hughsk flat up to 5.0.0. This affects the function unflatten of the file index.js. The manipulation leads to improperly controlled modification of object prototype attributes ('prototype pollution'). It is possible to initiate the attack remotely. Upgrading to version 5.0.1 can address this issue. The name of the patch is 20ef0ef55dfa028caddaedbcb33efbdb04d18e13. It is recommended to upgrade the affected component. The identifier VDB-216777 was assigned to this vulnerability.

Affected software

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PlatformPackageVulnerable versionsFixed in
npm package flat < 1.6.2, >= 2.0.0, < 2.0.2, >= 3.0.0, < 3.0.1, >= 4.0.0, < 4.0.2, >= 5.0.0, < 5.0.1 1.6.2, 2.0.2, 3.0.1, 4.0.2, 5.0.1

References

CVSS score 9.8/10
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness (CWE)
CWE-1321
Platform
npm
Package
flat
Disclosed
25.12.2022
Updated
11.10.2026 10:22

Sources and licenses

OSV / GitHub Advisory Database - GHSA-2j2x-2gpw-g8fm - CC BY 4.0

Vulnerability history: flat

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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