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CVE-2026-55091

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

Description (CNA)

flat-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.

Affected (CNA)

Vendor / productVersions
joaonuno / flat-to-nested-jsaffected < 1.1.2

CWE

CWE-915, CWE-1321

References

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.