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CVE Record

CVE-2021-23438: Prototype Pollution

This affects the package mpath before 0.8.4. A type confusion vulnerability can lead to a bypass of CVE-2018-16490. In particular, the condition ignoreProperties.indexOf(parts[i]) !== -1 returns -1 if parts[i] is ['__proto__']. This is because the method that has been called if the input is an array is Array.prototype.indexOf() and not String.prototype.indexOf(). They behave differently depending on the type of the input.

MediumCVSS 5.6Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2021-23438 affects mpath before 0.8.4. A flaw in how it checks blocked property names can allow prototype pollution in certain inputs. Business urgency is moderate: impact is limited by high attack complexity, but exposed applications should update because prototype pollution can undermine application logic.

Executive priority

Treat as a scheduled remediation item unless exposed in a high-risk application path. The issue is not known exploited from the provided evidence, but prototype pollution can create hard-to-predict application behavior, so dependency updates should not be deferred indefinitely.

Technical view

mpath has a type confusion issue in its property filtering logic. An array-shaped path segment can bypass the intended ignoreProperties check because Array.prototype.indexOf behaves differently from String.prototype.indexOf. The CVE describes this as a bypass of CVE-2018-16490, with potential low confidentiality, integrity, and availability impact.

Likely exposure

Exposure is most likely in applications or packaged dependencies using mpath versions before 0.8.4, including transitive JavaScript dependencies and referenced WebJars npm packaging. Evidence does not identify specific downstream products beyond mpath.

Exploitation context

The source bundle marks KEV as false and provides no evidence of active exploitation. CVSS lists network attack vector, no privileges, no user interaction, and high attack complexity. Exploit maturity is listed as proof-of-concept in the CVSS vector metadata.

Researcher notes

Focus validation on dependency resolution and package provenance. The key root cause is the mismatch between array and string indexOf behavior in the ignoreProperties check. The GitHub commit is the primary public code-change reference; sources do not provide product-specific exploitability conditions.

Mitigation direction

  • Upgrade mpath to version 0.8.4 or later.
  • Update transitive dependencies that bundle vulnerable mpath versions.
  • Check Snyk or vendor advisories for ecosystem-specific upgrade guidance.
  • Prioritize internet-facing applications that process untrusted object paths.

Validation and detection

  • Inventory direct and transitive dependencies for mpath before 0.8.4.
  • Check Java WebJars npm packages for vulnerable mpath packaging.
  • Confirm lockfiles resolve mpath to 0.8.4 or later.
  • Review SCA results for CVE-2021-23438 after updating.
Prepared
Confidence
high
Sources
5

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.

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CVE-2021-23438 mapping review

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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
4Source 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-2021-23438Attack 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/ampathunspecifiedListed
Weakness

CWE details

No CWE listed

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