What is CVE-2020-36632?

CVE-2020-36632 is a medium-severity vulnerability in Flat Project, classified under Improperly Controlled Modification of Object Prototype Attributes (Prototype Pollution). CVSS score: 6.3/10. Published 2022-12-25.

How severe is CVE-2020-36632?

Medium severity. CVSS v3 base score is 6.3 out of 10.

Is CVE-2020-36632 known to be exploited?

4 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Prototype Pollution in Flat Project

CVE-2020-36632

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 is able to 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.

Vulnerability class: Prototype Pollution

Published 2022-12-25 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L.

EPSS exploit prediction

EPSS: 0.011 (64.8th percentile), scored 2026-10-02.

Low probability of exploitation in the next 30 days, but still tracked. 65th percentile — 64.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.011 · newest: 0.011 · change: 0.000

Affected products

Flat Project
Hughsk Flat — versions 5.0

Weakness classification (CWE)

CWE-1321 — Improperly Controlled Modification of Object Prototype Attributes (Prototype Pollution)

Public proof-of-concept exploits

References

vuldb.com/ (technical-description, Third Party Advisory, vdb-entry)
vuldb.com/ (signature, permissions-required, Third Party Advisory)
github.com/hughsk/flat/issues/105 (issue-tracking, Third Party Advisory, Issue Tracking)
github.com/hughsk/flat/pull/106 (issue-tracking, Patch, Third Party Advisory)
github.com/hughsk/flat/commit/20ef0ef55dfa028caddaedbcb33efbdb04d18e13 (Patch, Third Party Advisory, patch)
github.com/hughsk/flat/releases/tag/5.0.1 (Third Party Advisory, Release Notes, patch)

Frequently asked questions

What is CVE-2020-36632?: CVE-2020-36632 is a medium-severity vulnerability in Flat Project, classified under Improperly Controlled Modification of Object Prototype Attributes (Prototype Pollution). CVSS score: 6.3/10. Published 2022-12-25.
How severe is CVE-2020-36632?: Medium severity. CVSS v3 base score is 6.3 out of 10.
Is CVE-2020-36632 known to be exploited?: 4 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.