The vulnerability occurs in the experimental tasks (taskStore) of the MCP TypeScript SDK between versions 1.24.0 and 1.31.x. It allows a client that shares an InMemoryTaskStore with other clients to view, read, and cancel tasks created by those other clients, violating isolation of tasks. The weakness is due to missing session validation, which is a session-based authorization flaw. The impact can lead to unauthorized read or deletion of tasks and potentially compromise data confidentiality and integrity for shared task data.

Vendors are Model Context Protocol for their TypeScript SDK. Affected products are the TypeScript SDK for Model Context Protocol servers and clients. The vulnerability affects all SDK releases from version 1.24.0 up to but excluding 1.32.0. A patch is available in version 1.32.0 and later.

The CVSS score of 8.6 indicates high severity. No EPSS score is available, so the exact exploitation probability is unknown, but the lack of session checks likely makes it easy for an attacker who can inject code or share an InMemoryTaskStore to exploit. Because the issue is not listed in CISA KEV, there is no indication of an active exploit campaign yet. Attackers could target any client that shares the same task store with a malicious user, leading to possible information disclosure or task cancellation.