CVE-2021-3645Public exploitNetwork attack vector

Object prototype modification via unchecked merge keys

Published Sep 10, 2021 · Updated Aug 3, 2024

Prototype pollution in @viking04/merge before 1.0.2 allows context-dependent attackers to modify Object.prototype via crafted merge input. The merge function recursively processes enumerable source keys without rejecting proto or constructor, allowing a crafted source object to write inherited properties. Exploitation requires a consuming application to pass attacker-controlled objects to merge, and the resulting consequence depends on prototype gadgets in that application.

CVSS severity6.8
Medium
EPSS probability1.43%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Prototype pollution in @viking04/merge before 1.0.2 allows context-dependent attackers to modify Object.prototype via crafted merge input. The merge function recursively processes enumerable source keys without rejecting proto or constructor, allowing a crafted source object to write inherited properties. Exploitation requires a consuming application to pass attacker-controlled objects to merge, and the resulting consequence depends on prototype gadgets in that application.

The record

CVE
CVE-2021-3645
Published
Sep 10, 2021
Updated
Aug 3, 2024
Vendor
Viking04
Product
@viking04/merge
Classifications
CWE-1321
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 10, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <1.0.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Viking04 · @viking04/mergeversion=unspecified <1.0.2

Published CVSS scores

6.8huntr.dev CNACVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
7.5NIST NVDAV:N/AC:L/Au:N/C:P/I:P/A:P
9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

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

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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