CVE-2021-23820Public exploitNetwork attack vector

Prototype pollution via array pointer components

Published Nov 3, 2021 · Updated Sep 16, 2024

Type confusion in json-pointer through 0.6.1 allows remote attackers to modify object prototypes via crafted JSON Pointer arrays. The pointer.set routine treats array-valued pointer components as property keys without enforcing primitive string or number types, allowing a nested proto component to bypass the earlier pollution fix. Exploitation requires an application to pass attacker-controlled pointer arrays into this routine; successful requests can alter inherited properties and potentially affect confidentiality, integrity, and availability.

CVSS severity9.8
Critical
EPSS probability1.87%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Type confusion in json-pointer through 0.6.1 allows remote attackers to modify object prototypes via crafted JSON Pointer arrays. The pointer.set routine treats array-valued pointer components as property keys without enforcing primitive string or number types, allowing a nested proto component to bypass the earlier pollution fix. Exploitation requires an application to pass attacker-controlled pointer arrays into this routine; successful requests can alter inherited properties and potentially affect confidentiality, integrity, and availability.

The record

CVE
CVE-2021-23820
Published
Nov 3, 2021
Updated
Sep 16, 2024
Vendor
Manuel Stofer
Product
json-pointer
Classifications
CWE-843
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 3, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 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?

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  1. Affected versionversion=0 <unspecified

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Manuel Stofer · json-pointerversion=0 <unspecified

Published CVSS scores

5.6SnykCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L
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.

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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-843Access of Resource Using Incompatible Type ('Type Confusion')

Public exploit references

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Technologies

Your stack

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Your stack

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