Seroval facilitates JavaScript value stringification, including complex structures beyond JSON.stringify capabilities. Prior to 1.6.8, fromJSON rebuilds an AsyncIteratorFactoryInstance by calling source.on(listener) without requiring source to be a genuine internal stream. With untrusted Seroval input and an application plugin that returns a callable value or an object exposing an on method, a crafted node can reuse an identifier so the deserializer invokes the plugin-produced value. This is an incomplete-fix variant of CVE-2026-59940. The resulting confidentiality, integrity, or availability impact depends on the behavior exposed by the application plugin. This issue is fixed in version 1.6.8.