CVE-2021-4245Public exploit

Prototype pollution via unsafe JSON Pointer traversal

Published Dec 15, 2022 · Updated Aug 3, 2024

Prototype pollution in Christopher Brown's rfc6902 before 5.0.0 allows context-dependent attackers to modify Object.prototype via crafted patch paths. Pointer.get in pointer.ts traverses each decoded token and previously looked up proto, constructor, and prototype on the current object instead of rejecting or skipping those keys. A consuming application must pass an attacker-controlled path to applyPatch; polluted inherited properties can then alter application behavior, while downstream impact depends on application use.

CVSS severity9.8
Critical
EPSS probability1.27%
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 Christopher Brown's rfc6902 before 5.0.0 allows context-dependent attackers to modify Object.prototype via crafted patch paths. Pointer.get in pointer.ts traverses each decoded token and previously looked up proto, constructor, and prototype on the current object instead of rejecting or skipping those keys. A consuming application must pass an attacker-controlled path to applyPatch; polluted inherited properties can then alter application behavior, while downstream impact depends on application use.

The record

CVE
CVE-2021-4245
Published
Dec 15, 2022
Updated
Aug 3, 2024
Vendor
Christopher Brown
Product
rfc6902
Classifications
CWE-74, CWE-1321
Attack vector
Unavailable
Privileges
Unavailable

Timeline

How it unfolded

  1. Dec 15, 2022CVE 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=n/a

What conditions does exploitation require?

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

What is affected?

Christopher Brown · rfc6902version=n/a

Published CVSS scores

9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
5.5VulDBCVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L

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-74Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
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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