Cross-Client Data Leak in MCP TypeScript SDK Version 1.10.0 to 1.25.3
CVE-2026-25536

7.1HIGH

Key Information:

Vendor

Modelcontextprotocol

Status
Typescript-sdk
Vendor
CVE Published:
4 February 2026

What is CVE-2026-25536?

The MCP TypeScript SDK, designed for Model Context Protocol servers and clients, suffers from a vulnerability that allows data leakage across different client connections when a single McpServer/Server instance is reused. This is particularly prevalent in stateless StreamableHTTPServerTransport setups. When clients share the server/transport, sensitive response data from one client can be inadvertently exposed to another. This issue affects versions 1.10.0 through 1.25.3 and has been addressed in version 1.26.0.

Affected Version(s)

typescript-sdk >= 1.10.0, < 1.26.0

References

https://github.com/modelcontextprotocol/typescript-sdk/se...
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https://github.com/modelcontextprotocol/typescript-sdk/is...
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https://github.com/modelcontextprotocol/typescript-sdk/is...
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CVSS V3.1

Score:
7.1
Severity:
HIGH
Confidentiality:
High
Integrity:
Low
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.