What is CVE-2021-23561?

CVE-2021-23561 is a medium-severity vulnerability in C2fo Comb, classified under Improperly Controlled Modification of Object Prototype Attributes (Prototype Pollution). CVSS score: 6.5/10. Published 2021-12-10.

How severe is CVE-2021-23561?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Prototype Pollution in C2fo Comb

CVE-2021-23561

All versions of package comb are vulnerable to Prototype Pollution via the deepMerge() function.

Vulnerability class: Prototype Pollution

Published 2021-12-10 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L.

EPSS exploit prediction

EPSS: 0.012 (68.2th percentile), scored 2026-10-24.

Low probability of exploitation in the next 30 days, but still tracked. 68th percentile — 68.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.012 · newest: 0.012 · change: +0.000

Affected products

C2fo Comb
Comb — versions 0

Weakness classification (CWE)

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

References

snyk.io/vuln/SNYK-JS-COMB-1730083 (Exploit, Third Party Advisory, Mitigation)

Frequently asked questions

What is CVE-2021-23561?: CVE-2021-23561 is a medium-severity vulnerability in C2fo Comb, classified under Improperly Controlled Modification of Object Prototype Attributes (Prototype Pollution). CVSS score: 6.5/10. Published 2021-12-10.
How severe is CVE-2021-23561?: Medium severity. CVSS v3 base score is 6.5 out of 10.