Prototype Pollution

published 2020-12-22 5 y ago modified 2026-06-17 4 mo ago also GHSA-g78f-549w-c354 , EUVD-2021-0823

cvss: 5.6; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 1.5%; EPSS 1.5% chance of exploitation in 30 days, percentile 73%
public exploits: 0; none known

This affects the package multi-ini before 2.1.1. It is possible to pollute an object's prototype by specifying the proto object as part of an array.

Patch / fix

fixed in 2

npm multi-ini 2.1.1
n/a multi-ini 2.1.1

Exploit prediction

1.46% chance of exploitation in the next 30 days, higher than 73% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/evangelion1204/multi-ini/pull/37 referenced PoC, tagged "exploit" by a source, unverified
snyk.io https://snyk.io/vuln/SNYK-JS-MULTIINI-1048969 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	3.1	5.6	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L/E:P/RL:O/RC:R
CNA	3.1	5.6	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L
NVD	3.1	9.8	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD	2.0	7.5	AV:N/AC:L/Au:N/C:P/I:P/A:P
GitHub	3.1	9.8	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected packages

ecosystem	package	affected	fixed in
npm	multi-ini	<2.1.1	2.1.1

Affected products

n/a multi-ini

Classification

Weakness

CWE-1321 Improperly Controlled Modification of Object Prototype Attributes

References

github.com /evangelion1204/multi-ini/pull/37
web, exploit, third-party-advisory
snyk.io /vuln/SNYK-JS-MULTIINI-1048969
web, exploit, third-party-advisory
nvd.nist.gov /vuln/detail/CVE-2020-28448
advisory

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary