Junglewise Threat Intelligence

CVE-2026-33228: WebReflection flatted prototype pollution in parse function

CVE-2026-33228 · Severity: critical · CVSS 9.8 · Published 2026-03-20

Technologies: Red Hat build of Keycloak, Red Hat build of Keycloak, Red Hat Developer Hub. Vendors: npm, Red Hat.

Executive brief

Flatted is a software library used to process complex data structures in JavaScript applications. A security flaw allows an attacker to send specially crafted data that can corrupt the application's internal memory. This can lead to a complete system takeover, data theft, or a total service outage.

Technical details

A prototype pollution vulnerability exists in the parse() function of the flatted library due to improper validation of array index keys. The parser uses attacker-controlled string values from the input JSON as direct keys for an internal JavaScript Array buffer. By providing the key '__proto__', an attacker can obtain a live reference to Array.prototype. Subsequent operations that write to properties of the parsed object can then modify the global prototype chain. This can be exploited remotely without authentication to achieve arbitrary code execution or denial of service. The issue is fixed in version 3.4.2 by ensuring index keys are validated as numeric and within bounds.

Affected products

  • WebReflection flatted <= 3.4.1
  • Red Hat Red Hat Developer Hub 1.8
  • Red Hat Red Hat Developer Hub 1.9
  • Red Hat Red Hat 3scale API Management Platform 2
  • Red Hat Red Hat Build of Keycloak
  • Red Hat Red Hat Single Sign-On 7

Timeline

  • 2026-03-17: patched: Version 3.4.2 released
  • 2026-03-19: advisory: GitHub Security Advisory GHSA-rf6f-7fwh-wjgh published
  • 2026-03-20: disclosed: CVE-2026-33228 published to NVD

References

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