Effect-TS effect up to 3.19.x API Call race condition

Summaryinfo

A vulnerability, which was classified as problematic, has been found in Effect-TS effect up to 3.19.x. Affected by this vulnerability is the function RpcServer.toWebHandler/HttpApp.toWebHandlerRuntime of the component API Call Handler. Performing a manipulation results in race condition. This vulnerability was named CVE-2026-32887. The attack may be initiated remotely. There is no available exploit. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic has been found in Effect-TS effect up to 3.19.x. This affects the function RpcServer.toWebHandler/HttpApp.toWebHandlerRuntime of the component API Call Handler. The manipulation with an unknown input leads to a race condition vulnerability. CWE is classifying the issue as CWE-362. The product contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

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.

It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2026-32887 since 03/16/2026. The exploitability is told to be difficult. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details of the vulnerability are known, but there is no available exploit.

Upgrading to version 3.20.0 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-13818). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Vendor

• Effect-TS

Name

• effect

Version

• 3.0
• 3.1
• 3.2
• 3.3
• 3.4
• 3.5
• 3.6
• 3.7
• 3.8
• 3.9
• 3.10
• 3.11
• 3.12
• 3.13
• 3.14
• 3.15
• 3.16
• 3.17
• 3.18
• 3.19

Website

• Product: https://github.com/Effect-TS/effect/

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Be aware that VulDB is the high quality source for vulnerability data.

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