Prototype Pollution in async merge-object

published 2018-07-03 8 y ago modified 2026-06-17 4 mo ago also GHSA-fp82-2h99-3fpp , EUVD-2018-0455

cvss: 9.8; version 3.0, NVD
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

The utilities function in all versions <= 1.0.0 of the merge-objects node module can be tricked into modifying the prototype of Object when the attacker can control part of the structure passed to this function. This can let an attacker add or modify existing properties that will exist on all objects.

Exploit prediction

1.43% chance of exploitation in the next 30 days, higher than 73% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

hackerone.com https://hackerone.com/reports/310706 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
NVD	3.0	9.8	CVSS:3.0/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	3.0	9.8	CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected packages

ecosystem	package	affected	fixed in
npm	merge-object	<=1.0.0	no fix listed

Classification

Weakness

CWE-20 Improper Input Validation
CWE-1321 Improperly Controlled Modification of Object Prototype Attributes

References

hackerone.com /reports/310706
web, exploit, issue-tracking, third-party-advisory
nvd.nist.gov /vuln/detail/CVE-2018-3753
advisory

Sources

CVE List CVE-2018-3753
GitHub Advisory GHSA-fp82-2h99-3fpp
NVD CVE-2018-3753

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