What happened
The official MCP TypeScript SDK, from 1.24.0 to before 1.32.0, did not verify which session created a task in the experimental tasks feature (taskStore). Clients sharing one InMemoryTaskStore could list, read and cancel each other's tasks. The issue is patched in 1.32.0.
Why it matters
The MCP TypeScript SDK is the official client/server SDK used across the agent ecosystem. A missing session-scope check on task storage lets one session observe and cancel another session's long-running tasks, which can leak task payloads/state across agent sessions or abrogate concurrent workflows where sessions are meant to be isolated.
Attack vector
One MCP client session lists/reads/cancels another session's tasks in a shared task store
Affected systems
modelcontextprotocol/typescript-sdk 1.24.0 up to but excluding 1.32.0 (experimental taskStore/InMemoryTaskStore)
Mitigation
Upgrade to @modelcontextprotocol/sdk 1.32.0 or later