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CVE Record

CVE-2021-23426: Prototype Pollution

This affects all versions of package Proto. It is possible to inject pollute the object property of an application using Proto by leveraging the merge function.

MediumCVSS 5.6Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2021-23426 is a prototype pollution issue in the npm package Proto. If an application uses Proto's merge function on attacker-controlled data, an attacker may alter shared object properties and affect confidentiality, integrity, or availability. The published severity is medium, not critical.

Executive priority

Medium priority. This should be handled through dependency inventory and planned remediation, with faster action for internet-facing applications that merge user-supplied data. There is no KEV listing or source-bundle evidence of active exploitation.

Technical view

The source bundle describes all versions of Proto as affected by prototype pollution through its merge function. The CVSS 3.1 vector is 5.6 medium: network attack vector, high complexity, no privileges, no user interaction, unchanged scope, and low confidentiality, integrity, and availability impact.

Likely exposure

Exposure is most likely in JavaScript or Node.js applications that depend on Proto and use its merge function with untrusted input. The bundle does not identify specific downstream products, deployments, or vulnerable application patterns beyond Proto usage.

Exploitation context

The CVSS vector lists proof-of-concept exploit maturity, but the bundle does not state active exploitation. CISA KEV is false. Treat this as a real dependency risk requiring inventory and remediation review, not evidence of known in-the-wild attacks.

Researcher notes

Evidence is limited to the CVE metadata and referenced Proto/Snyk pages in the bundle. The affected range is described as all versions, but no specific fixed version or mitigation is included here. Do not assume downstream exploitability without confirming merge usage and input control.

Mitigation direction

  • Check vendor, npm, and Snyk guidance for a maintained fixed release or replacement path.
  • Remove or replace Proto where no supported safe version is available.
  • Avoid passing untrusted objects into Proto's merge function.
  • Add input validation around object merge boundaries handling external data.
  • Prioritize remediation for internet-facing services using Proto in request processing.

Validation and detection

  • Search dependency manifests and lockfiles for the Proto package.
  • Confirm whether production builds actually include Proto.
  • Review code paths that call Proto's merge function.
  • Identify whether attacker-controlled input can reach those merge calls.
  • Check current advisory sources for any named fixed version or vendor guidance.
Prepared
Confidence
medium
Sources
4

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

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CVE-2021-23426 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:U/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
3Source 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:U/RC:C2.23.4Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

5.6Medium
CVSS 3.1 vector shape for CVE-2021-23426Attack 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:U/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/aProto0Listed
Weakness

CWE details

No CWE listed

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