CVE-2026-25536 PUBLISHED

@modelcontextprotocol/sdk has cross-client data leak via shared server/transport instance reuse

Assigner: GitHub_M
Reserved: 02.02.2026 Published: 04.02.2026 Updated: 04.02.2026

MCP TypeScript SDK is the official TypeScript SDK for Model Context Protocol servers and clients. From version 1.10.0 to 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.

Metrics

CVSS 3.1

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N
CVSS Score: 7.1

Attack Vector	Network	Scope	Unchanged
Attack Complexity	Low	Confidentiality Impact	High
Privileges Required	Low	Integrity Impact	Low
User Interaction	None	Availability Impact	None

CVSS 3.1

Product Status

Vendor	modelcontextprotocol
Product	typescript-sdk
Versions	Version >= 1.10.0, < 1.26.0 is affected

References

Problem Types

CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') CWE