Prototype Pollution

published 2021-02-18 5 y ago modified 2026-06-17 4 mo ago also GHSA-7wpw-2hjm-89gp , EUVD-2021-1010

cvss: 7.3; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 1.4%; EPSS 1.4% chance of exploitation in 30 days, percentile 73%
public exploits: 0; none known

All versions of package merge are vulnerable to Prototype Pollution via _recursiveMerge .

Patch / fix

fixed in 2 links 1

npm merge 2.1.1
merge_project merge 2.1.1

github.com/yeikos/js.merge@7b0ddc2 commit

Exploit prediction

1.44% chance of exploitation in the next 30 days, higher than 73% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	7.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L/E:P
CNA	3.1	7.3	CVSS:3.1/AV:N/AC:L/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	7.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

Affected packages

ecosystem	package	affected	fixed in
npm	merge	<2.1.1	2.1.1

Affected products

n/a merge

Classification

Weakness

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

References

github.com /yeikos/js.merge/commit/7b0ddc2701d813f2ba289b32d6a4b9d4cc235fb4
web
snyk.io /vuln/SNYK-JS-MERGE-1042987
web, broken-link
snyk.io /vuln/SNYK-JAVA-ORGWEBJARSNPM-1071049
web, broken-link
github.com /yeikos/js.merge/blob/master/src/index.ts%23L64
broken-link
nvd.nist.gov /vuln/detail/CVE-2020-28499
advisory
github.com /yeikos/js.merge/blob/56ca75b2dd0f2820f1e08a49f62f04bbfb8c5f8f/src/index.ts#L64
web
github.com /yeikos/js.merge/blob/master/src/index.ts#L64
web
vuldb.com /?id.170146
web, third-party-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