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Vulnerability · Published Feb 4, 2026 · Assigned by GitHub_M

CVE-2026-25536@modelcontextprotocol/sdk has cross-client data leak via shared server/transport instance reuse

High 7.1

In plain English

A high-severity race condition in typescript-sdk from modelcontextprotocol. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 22% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.1High
Exploit odds (30 days)0.3%top 78.0% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
npm@modelcontextprotocol/sdk1.26.0GHSA-345p-7cg4-v4c7

Affected products (as reported)

VendorProductVersions
modelcontextprotocol typescript-sdk >= 1.10.0, < 1.26.0

Weakness: CWE-362, CWE-367 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N

References