flat-to-nested: Prototype pollution in flat-to-nested convert() via __proto__ parent/id key

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-55091
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-14 18:17:54 UTC
Updated2026-09-30 17:51:56 UTC
Descriptionflat-to-nested converts a hierarchy from a flat representation to a nested representation. Prior to 1.1.2, FlatToNested.prototype.convert in index.js uses attacker-influenced id and parent record fields directly as keys in the plain temp and pendingChildOf objects. When parent or id is __proto__, temp[parent] can resolve to Object.prototype, and initPush() can write attacker-controlled data to the global children prototype property while existing prototype methods remain intact. Any application that passes attacker-influenced flat records to convert() can therefore expose unrelated objects to polluted inherited state, causing application-logic corruption or denial of service and potentially enabling greater impact when a downstream prototype-pollution gadget is present. The constructor and prototype strings are also unsafe inherited-key values in the same lookup design. This issue is fixed in version 1.1.2.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

EPSS: 0.004970000 probability, percentile 0.423530000 (date 2026-10-26)

Problem Types: CWE-915 | CWE-1321 | CWE-915 CWE-915: Improperly Controlled Modification of Dynamically-Determined Object Attributes | CWE-1321 CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
3.1CNADECLARED7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Joaonuno Flat-to-nested-js affected < 1.1.2 Not specified

References

ReferenceSourceLinkTags
github.com/joaonuno/flat-to-nested-js/commit/680a5ebe1194edda16fa93baaa5... [email protected] github.com
github.com/joaonuno/flat-to-nested-js/security/advisories/GHSA-hp36-v28f... [email protected] github.com
github.com/joaonuno/flat-to-nested-js/releases/tag/v1.1.2 [email protected] github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

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