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AI agent vulnerability · MCP TypeScript SDK

CVE-2026-111767: MCP TypeScript SDK: Experimental tasks were not tied to the session that created them

highCVSS 3.1 8.6GHSA-22jm-h49p-29qw

Summary In affected versions, the experimental tasks feature (taskStore) did not check which session created a task. Clients sharing one InMemoryTaskStore could list, read and cancel each other's tasks. Experimental tasks are deprecated. The 2026-07-28 specification replaced them with a redesigned extension. The best course of action is to stop using them.

Published Oct 20, 2026

Affected packages

@modelcontextprotocol/sdk

Ecosystem
npm
Affected
>= 1.24.0, < 1.32.0
Fixed in
1.32.0
Check
npm ls @modelcontextprotocol/sdk

Advisory details

From the GitHub Advisory Database (CC BY 4.0).

Summary

In affected versions, the experimental tasks feature (taskStore) did not check which session created a task. Clients sharing one InMemoryTaskStore could list, read and cancel each other's tasks.

Experimental tasks are deprecated. The 2026-07-28 specification replaced them with a redesigned extension. The best course of action is to stop using them.

Am I affected?

Only if your HTTP server passes taskStore to McpServer or Server. If grep -ri taskstore --exclude-dir=node_modules . finds nothing, you are not affected.

Affected versions: @modelcontextprotocol/sdk 1.24.0 through 1.31.0. The 2.x packages are not affected.

Fix

Upgrade to @modelcontextprotocol/sdk 1.32.0 or later. Each task is now tied to the session that created it, so a client that starts a new session can no longer reach its earlier tasks.

If you cannot upgrade yet, remove taskStore, or create one InMemoryTaskStore per session.

Credited to cipher-creator.

References

How this page is made: the data panel comes from the GitHub Advisory Database, CISA’s KEV catalog, the NVD and FIRST EPSS, and updates twice a day. No analysis has been written for this entry yet. Methodology

Coverage on the Beam blog

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