CVE-2026-25536: CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') in modelcontextprotocol typescript-sdk
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.
AI Analysis
Technical Summary
The modelcontextprotocol TypeScript SDK suffers from a concurrency issue where improper synchronization leads to a race condition. Specifically, when a single McpServer/Server and transport instance is shared across multiple client connections, response data can leak between clients. This vulnerability affects versions from 1.10.0 up to and including 1.25.3. The problem is resolved in version 1.26.0, which includes a fix to prevent cross-client data leakage by properly synchronizing access to shared resources.
Potential Impact
Exploitation of this vulnerability can result in unauthorized disclosure of response data across different clients connected to the same server instance. This compromises confidentiality (high impact on confidentiality) but does not affect integrity or availability. The CVSS 3.1 base score is 7.1 (High), reflecting network attack vector, low attack complexity, requiring low privileges, no user interaction, and impact limited to confidentiality.
Mitigation Recommendations
An official fix is available in version 1.26.0 of the modelcontextprotocol TypeScript SDK. Users should upgrade to version 1.26.0 or later to remediate this vulnerability. There are no vendor advisories indicating that no action is required or that the issue is otherwise mitigated. Patch status is confirmed by the vendor advisory.
CVE-2026-25536: CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') in modelcontextprotocol typescript-sdk
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.
CVSS v3.1
Score 7.1high
Affected software
pkg:github/modelcontextprotocol/typescript-sdkRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The modelcontextprotocol TypeScript SDK suffers from a concurrency issue where improper synchronization leads to a race condition. Specifically, when a single McpServer/Server and transport instance is shared across multiple client connections, response data can leak between clients. This vulnerability affects versions from 1.10.0 up to and including 1.25.3. The problem is resolved in version 1.26.0, which includes a fix to prevent cross-client data leakage by properly synchronizing access to shared resources.
Potential Impact
Exploitation of this vulnerability can result in unauthorized disclosure of response data across different clients connected to the same server instance. This compromises confidentiality (high impact on confidentiality) but does not affect integrity or availability. The CVSS 3.1 base score is 7.1 (High), reflecting network attack vector, low attack complexity, requiring low privileges, no user interaction, and impact limited to confidentiality.
Mitigation Recommendations
An official fix is available in version 1.26.0 of the modelcontextprotocol TypeScript SDK. Users should upgrade to version 1.26.0 or later to remediate this vulnerability. There are no vendor advisories indicating that no action is required or that the issue is otherwise mitigated. Patch status is confirmed by the vendor advisory.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-02-02T19:59:47.374Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Vendor Advisory Urls
- [{"url":"https://access.redhat.com/security/cve/CVE-2026-25536","vendor":"Red Hat"},{"url":"https://access.redhat.com/errata/RHSA-2026:3960","vendor":"Red Hat"}]
Threat ID: 6983bde5f9fa50a62fae8c8f
Added to database: 02/04/2026, 21:45:09 UTC
Last enriched: 07/15/2026, 08:39:53 UTC
Last updated: 09/10/2026, 19:50:01 UTC
Views: 529
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