CVE-2021-3645: merge is vulnerable to Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution

This week

CRITICAL 9.8REMOTEUPGRADE

CVE-2021-3645 is a critical-severity flaw (CVSS 9.8) affecting merge. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

merge is vulnerable to Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

Why this priority

Critical severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.4% (top 27%)
CISA exploited list	No
Weakness	CWE-1321
Published	2021-09-10
Last modified	2026-06-17

Publisher (CNA): huntr.dev · Vendor: merge project

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-09-10 11:15 UTCPublished CVE record published
2026-06-17 04:05 UTCUpdated Record last modified

merge project merge UPGRADE

Affected: < 1.0.2

Fixed in: 1.0.2

Safe to downgrade to: no unaffected older release

1. Check installed version

npm ls merge

2. UPGRADE to 1.0.2

npm install merge@">=1.0.2"

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-3645?

merge: upgrade to 1.0.2. Exact commands for each OS are on this page.

Is CVE-2021-3645 being exploited?

CVE-2021-3645 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-3645 affect?

CVE-2021-3645 affects merge. Severity is critical (CVSS 9.8). merge is vulnerable to Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

How urgent is CVE-2021-3645?

Priority 63/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2021-23397 MEDIUM 5.6 MITIGATE All versions of package @ianwalter/merge are vulnerable to Prototype Pollution via the main (merge) function
CVE-2020-28499 HIGH 7.3 UPGRADE All versions of package merge are vulnerable to Prototype Pollution via _recursiveMerge .

References

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