CVE-2026-33228

Fixed in a distro release EPSS <1%CVSS 8.9

flatted is a circular JSON parser. Prior to version 3.4.2, the parse() function in flatted can use attacker-controlled string values from the parsed JSON as direct array index keys, without validating that they are numeric. Since the internal input buffer is a JavaScript Array, accessing it with the key "__proto__" returns Array.prototype via the inherited getter. This object is then treated as a legitimate parsed value and assigned as a property of the output object, effectively leaking a live reference to Array.prototype to the consumer. Any code that subsequently writes to that property will pollute the global prototype. This issue has been patched in version 3.4.2.

Published 2026-03-20 · CVE record · OSV

Products: WebReflection flatted, Red Hat Cluster Observability Operator 1.5.0, Red Hat Developer Hub 1.8, Red Hat Developer Hub 1.9, Red Hat Cryostat 4, Logging Subsystem for Red Hat OpenShift, Red Hat Multicluster Engine for Kubernetes, Red Hat 3scale API Management Platform 2, Red Hat Advanced Cluster Management for Kubernetes 2, Red Hat AMQ Broker 7, Red Hat build of Apicurio Registry 2, Red Hat Build of Keycloak, Red Hat build of OptaPlanner 8, Red Hat Build of Podman Desktop, Red Hat Data Grid 8, Red Hat Directory Server 11, Red Hat Directory Server 12, Red Hat Directory Server 13, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat Fuse 7, Red Hat JBoss Enterprise Application Platform 7, Red Hat JBoss Enterprise Application Platform 8, Red Hat JBoss Enterprise Application Platform Expansion Pack, Red Hat OpenShift AI (RHOAI), Red Hat OpenShift Container Platform 4, Red Hat Process Automation 7, Red Hat Quay 3, Red Hat Single Sign-On 7, Red Hat streams for Apache Kafka 2, Red Hat streams for Apache Kafka 3

Fixed upstream

Distro releases