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Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') in @modelcontextprotocol/sdk

CVE-2026-25536

  • @modelcontextprotocol/sdk
High
7.1/10

Summary

MCP TypeScript SDK is the official TypeScript SDK for Model Context Protocol servers and clients. From version 1.10.0 through 1.25.3, cross-client response data leak when a single McpServer/Server and transport instance is reused across multiple client connections, most commonly in stateless StreamableHTTPServerTransport deployments. This issue has been patched in version 1.26.0.

  • LOW
  • NETWORK
  • LOW
  • UNCHANGED
  • NONE
  • LOW
  • HIGH
  • NONE

CWE-362 - Race Condition

A race condition occurs in a shared memory program when two threads/processes access the same shared memory data, and at least one thread executes a write operation. This vulnerability manipulates the time to check vs. time to use (TOC/TOU) gap between the threads in the critical section to cause disorientation in the shared data. The impact can vary from compromising the confidentiality of the system to causing the system to crash or to execute arbitrary code.

References

Advisory Timeline

  • Published