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CVE Record

CVE-2021-23509: Prototype Pollution

This affects the package json-ptr before 3.0.0. A type confusion vulnerability can lead to a bypass of CVE-2020-7766 when the user-provided keys used in the pointer parameter are arrays.

MediumCVSS 5.6Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2021-23509 affects json-ptr before 3.0.0. A flaw in how the library handles certain user-provided pointer keys can bypass an earlier prototype pollution fix, potentially affecting confidentiality, integrity, and availability at low impact levels.

Executive priority

Treat as a moderate dependency hygiene issue. Prioritize remediation where json-ptr is reachable from external input or included in internet-facing services.

Technical view

The CVE describes a type confusion issue in json-ptr where array values used as pointer keys can bypass protections for CVE-2020-7766. The CVSS 3.1 score is 5.6 with network attack vector, high complexity, no privileges, and no user interaction.

Likely exposure

Exposure is most likely in JavaScript or WebJars applications that include json-ptr before 3.0.0 and process untrusted pointer parameters or keys.

Exploitation context

The source bundle does not show CISA KEV listing or active exploitation. The CVSS metadata indicates proof-of-concept maturity, but exploitation is high complexity and source evidence is limited.

Researcher notes

Evidence names json-ptr before 3.0.0 and a bypass of CVE-2020-7766 through array keys in the pointer parameter. No CWE mapping is provided in the bundle.

Mitigation direction

  • Inventory npm and WebJars dependencies for json-ptr.
  • Upgrade json-ptr to version 3.0.0 or later where supported.
  • Review vendor advisories and lockfiles for transitive json-ptr usage.
  • If upgrade is blocked, restrict untrusted input reaching pointer handling.

Validation and detection

  • Confirm scanners no longer report CVE-2021-23509.
  • Check package-lock, yarn.lock, pnpm-lock, and build artifacts for pre-3.0.0 json-ptr.
  • Verify application paths that pass user input into json-ptr.
  • Add regression tests for array-shaped pointer keys if the library is used directly.
Prepared
Confidence
medium
Sources
6

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

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CVE-2021-23509 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
Medium
CVSS
5.6 (3.1)
Known Exploited
No
Published

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

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
0Timeline events
0ADP providers
6Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
5.6CVSS 3.1MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L/E:P/RL:O/RC:C2.23.4Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

5.6Medium
CVSS 3.1 vector shape for CVE-2021-23509Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/ajson-ptrunspecifiedListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.