CVE-2026-111767: CWE-639: Authorization Bypass Through User-Controlled Key in modelcontextprotocol typescript-sdk

The Model Context Protocol (MCP) TypeScript SDK, from versions 1.24.0 up to but not including 1.32.0, contains an authorization bypass vulnerability in its experimental tasks feature (taskStore). Specifically, the SDK failed to check the session ownership of tasks stored in a shared InMemoryTaskStore, enabling unauthorized clients to access and manipulate tasks created by other clients. This flaw is identified as CWE-639 (Authorization Bypass Through User-Controlled Key) and CWE-862 (Missing Authorization). The vulnerability has been addressed and patched in version 1.32.0.

Exploiting this vulnerability allows unauthorized clients sharing the same InMemoryTaskStore to list, read, and cancel tasks created by other clients, potentially leading to unauthorized disclosure of task information and disruption of task processing. The CVSS 3.1 base score is 8.6 (high severity), reflecting network attack vector, low complexity, no privileges required, no user interaction, and impacts on confidentiality (high), integrity (low), and availability (low).

Upgrade to version 1.32.0 or later of the Model Context Protocol TypeScript SDK, where the authorization checks for task ownership have been implemented to prevent unauthorized access. No other mitigations are indicated as the issue is fixed in this official release.