CVE-2021-23807Public exploit

Prototype pollution via array pointer type confusion

Published Nov 3, 2021 · Updated Sep 16, 2024

Prototype pollution in Jan Lehnardt jsonpointer before 5.0.0 allows attackers to modify inherited properties via crafted pointer arrays. The setter compares array-valued path components directly with reserved strings, so JavaScript coerces them to dangerous property keys only after the strict-equality guard is bypassed. Reachability requires consuming code to pass attacker-controlled pointer components to the set operation; polluted properties can alter application behavior and data handling.

CVSS severity9.8
Critical
EPSS probability2.73%
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 Jan Lehnardt jsonpointer before 5.0.0 allows attackers to modify inherited properties via crafted pointer arrays. The setter compares array-valued path components directly with reserved strings, so JavaScript coerces them to dangerous property keys only after the strict-equality guard is bypassed. Reachability requires consuming code to pass attacker-controlled pointer components to the set operation; polluted properties can alter application behavior and data handling.

The record

CVE
CVE-2021-23807
Published
Nov 3, 2021
Updated
Sep 16, 2024
Vendor
Jan Lehnardt
Product
jsonpointer
Classifications
CWE-843
Attack vector
Unavailable
Privileges
Unavailable

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?

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

  1. Affected versionversion=unspecified <5.0.0

What conditions does exploitation require?

Attack vectorUnavailable in this record.
Required privilegesUnavailable in this record.

What is affected?

Jan Lehnardt · jsonpointerversion=unspecified <5.0.0

Published CVSS scores

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

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)
VectorUnavailable
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

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

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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