CVE-2026-55091
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.
Scoring
- Severity
- HIGH
- CVSS base score
- 7.5
- CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
- EPSS probability
- 0.36%
- CWE
- CWE-915, CWE-1321
- Published
- 2026-09-14
- Last modified
- 2026-09-14
Affected products
- joaonuno flat-to-nested-js
Weakness type
Related vulnerabilities
- CVE-2025-68109 — ChurchCRM vulnerable to RCE with database restore functionality
- CVE-2022-4068 — Improperly Controlled Modification of Dynamically-Determined Object Attributes in librenms/librenms
- CVE-2026-27591 — Winter: Privilege escalation by authenticated backend users
- CVE-2025-58367 — DeepDiff is vulnerable to DoS and Remote Code Execution via Delta class pollution
- CVE-2024-5452 — RCE via Property/Class Pollution in lightning-ai/pytorch-lightning
- CVE-2026-33453 — Apache Camel: CoAP URI Query Parameter to Exchange Header Injection in camel-coap Allows Single-Packet Pre-Auth Remote Code Execution
- CVE-2026-22783 — Iris Allows Arbitrary File Deletion via Mass Assignment in Datastore File Management
- CVE-2026-12436 — Improperly Controlled Modification of Dynamically-Determined Object Attributes in GitLab