CVE-2021-23509Public exploitNetwork attack vector

Prototype pollution via array-valued pointer keys

Published Nov 3, 2021 · Updated Sep 16, 2024

Prototype pollution in Flitbit json-ptr before 3.0.0 allows remote attackers to alter inherited object properties via array pointer keys. JsonPointer.set validates a pointer segment before JavaScript coerces its array value to a forbidden prototype key, then writes through Object.prototype. Exploitation requires a consuming application to pass attacker-controlled pointer arrays to a set operation; the resulting pollution can change application behavior.

CVSS severity5.6
Medium
EPSS probability1.83%
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 Flitbit json-ptr before 3.0.0 allows remote attackers to alter inherited object properties via array pointer keys. JsonPointer.set validates a pointer segment before JavaScript coerces its array value to a forbidden prototype key, then writes through Object.prototype. Exploitation requires a consuming application to pass attacker-controlled pointer arrays to a set operation; the resulting pollution can change application behavior.

The record

CVE
CVE-2021-23509
Published
Nov 3, 2021
Updated
Sep 16, 2024
Vendor
Flitbit
Product
json-ptr
Classifications
CWE-1321, 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?

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

  1. Affected versionversion=unspecified <3.0.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Flitbit · json-ptrversion=unspecified <3.0.0

Published CVSS scores

5.1SnykCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L/E:P/RL:O/RC:C
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.

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-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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