CVE-2026-32887: Effectful Effect

High severity, CVSS 7.4. EPSS: 0.3% chance of exploitation in the next 30 days.

Effect is a TypeScript framework that consists of several packages that work together to help build TypeScript applications. Prior to version 3.20.0, when using `RpcServer.toWebHandler` (or `HttpApp.toWebHandlerRuntime`) inside a Next.js App Router route handler, any Node.js `AsyncLocalStorage`-dependent API called from within an Effect fiber can read another concurrent request's context — or no context at all. Under production traffic, `auth()` from `@clerk/nextjs/server` returns a different user's session. Version 3.20.0 contains a fix for the issue.

Affected products

• Effectful Effect: before 3.20.0 (fixed in 3.20.0)

Published 2026-03-20. Last modified 2026-06-17.