Prototype pollution vulnerability in js-extend

published 2021-05-26 5 y ago modified 2026-06-17 4 mo ago also GHSA-mh82-55cm-6gfh , EUVD-2021-1358

cvss: 9.8; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 3.0%; EPSS 3.0% chance of exploitation in 30 days, percentile 87%
public exploits: 0; none known

Prototype pollution vulnerability in 'js-extend' versions 0.0.1 through 1.0.1 allows attacker to cause a denial of service and may lead to remote code execution.

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-25945 updated 2025-11-21 cvss 8.2

js-extend: prototype pollution allows attacker to cause a denial of service and may lead to remote code execution

Red Hat All currently supported Red Hat products
not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

2.96% chance of exploitation in the next 30 days, higher than 87% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

whitesourcesoftware.com https://www.whitesourcesoftware.com/vulnerability-database/CVE-2021-25945 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
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	js-extend	<=1.0.1	no fix listed

Affected products

n/a js-extend

Classification

Weakness

CWE-1321 Improperly Controlled Modification of Object Prototype Attributes
CWE-915 Improperly Controlled Modification of Dynamically-Determined Object Attributes

References

whitesourcesoftware.com /vulnerability-database/CVE-2021-25945
web, exploit, third-party-advisory
nvd.nist.gov /vuln/detail/CVE-2021-25945
advisory
github.com /vmattos/js-extend
package

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