{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-55091", "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa", "state": "PUBLISHED", "assignerShortName": "GitHub_M", "dateReserved": "2026-06-16T14:41:54.578Z", "datePublished": "2026-09-14T17:26:38.877Z", "dateUpdated": "2026-09-14T20:05:59.070Z"}, "containers": {"cna": {"title": "flat-to-nested: Prototype pollution in flat-to-nested convert() via __proto__ parent/id key", "problemTypes": [{"descriptions": [{"cweId": "CWE-915", "lang": "en", "description": "CWE-915: Improperly Controlled Modification of Dynamically-Determined Object Attributes", "type": "CWE"}]}, {"descriptions": [{"cweId": "CWE-1321", "lang": "en", "description": "CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')", "type": "CWE"}]}], "metrics": [{"cvssV3_1": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 7.5, "baseSeverity": "HIGH", "confidentialityImpact": "NONE", "integrityImpact": "HIGH", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N", "version": "3.1"}}], "references": [{"name": "https://github.com/joaonuno/flat-to-nested-js/security/advisories/GHSA-hp36-v28f-w3r4", "tags": ["x_refsource_CONFIRM"], "url": "https://github.com/joaonuno/flat-to-nested-js/security/advisories/GHSA-hp36-v28f-w3r4"}, {"name": "https://github.com/joaonuno/flat-to-nested-js/commit/680a5ebe1194edda16fa93baaa56ff14fe0e3d7f", "tags": ["x_refsource_MISC"], "url": "https://github.com/joaonuno/flat-to-nested-js/commit/680a5ebe1194edda16fa93baaa56ff14fe0e3d7f"}, {"name": "https://github.com/joaonuno/flat-to-nested-js/releases/tag/v1.1.2", "tags": ["x_refsource_MISC"], "url": "https://github.com/joaonuno/flat-to-nested-js/releases/tag/v1.1.2"}], "affected": [{"vendor": "joaonuno", "product": "flat-to-nested-js", "versions": [{"version": "< 1.1.2", "status": "affected"}]}], "providerMetadata": {"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa", "shortName": "GitHub_M", "dateUpdated": "2026-09-14T17:26:38.877Z"}, "descriptions": [{"lang": "en", "value": "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."}], "source": {"advisory": "GHSA-hp36-v28f-w3r4", "discovery": "UNKNOWN"}}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"timestamp": "2026-09-14T19:22:11.687253Z", "id": "CVE-2026-55091", "options": [{"Exploitation": "none"}, {"Automatable": "yes"}, {"Technical Impact": "partial"}], "role": "CISA Coordinator", "version": "2.0.3"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-09-14T20:05:59.070Z"}}]}}

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