CVE-2021-25945Public exploitNetwork attack vector

Process crash or code execution via prototype pollution

Published May 26, 2021 · Updated Aug 3, 2024

Prototype pollution in Vitor Mattos js-extend 0.0.1 through 1.0.1 allows attackers to alter shared object prototypes via extend(). The extend() helper recursively enumerates source properties and assigns them to the destination without blocking the proto key. Exploitation requires an application to pass attacker-controlled object properties to the helper; polluted inherited properties can crash the process or enable code execution in a vulnerable consumer.

CVSS severity9.8
Critical
EPSS probability2.96%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Prototype pollution in Vitor Mattos js-extend 0.0.1 through 1.0.1 allows attackers to alter shared object prototypes via extend(). The extend() helper recursively enumerates source properties and assigns them to the destination without blocking the proto key. Exploitation requires an application to pass attacker-controlled object properties to the helper; polluted inherited properties can crash the process or enable code execution in a vulnerable consumer.

The record

CVE
CVE-2021-25945
Published
May 26, 2021
Updated
Aug 3, 2024
Vendor
Vitor Mattos
Product
js-extend
Classifications
CWE-1321, CWE-915
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 26, 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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=0.0.1, 0.0.2, 1.0.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Vitor Mattos · js-extendversion=0.0.1, 0.0.2, 1.0.1

Published CVSS scores

9.8NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.5NVDAV:N/AC:L/Au:N/C:P/I:P/A:P

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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

Public exploit references

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

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo