# CVE-2026-25536: CVE-2026-25536: MCP TypeScript SDK Cross-Client Data Leak

> CVE-2026-25536 is a high-severity information disclosure issue in @modelcontextprotocol/sdk, a MCP server. Affected: >=1.10.0 <1.26.0. Fixed in 1.26.0.

- **Canonical URL:** https://catalog.anomity.ai/vuln/cve-2026-25536
- **Aliases:** ti-003
- **Severity:** high
- **Attack type:** Information disclosure
- **Component:** @modelcontextprotocol/sdk (MCP server)
- **Package:** @modelcontextprotocol/sdk
- **Exploited in the wild:** no known exploitation
- **Published:** 2026-03-18
- **Last verified:** 2026-11-01
- **JSON:** https://catalog.anomity.ai/api/entries/vuln/cve-2026-25536

## Summary

When a single McpServer instance using StreamableHTTPServerTransport was reused across multiple HTTP clients, a common stateless deployment pattern, response routing could misfire and deliver one client's data to a different client entirely. Affected MCP SDK versions 1.10.0–1.25.3; fixed in 1.26.0. At disclosure, 82% of surveyed production MCP servers were running a vulnerable version.

## Affected versions

| Affected | Fixed in |
| --- | --- |
| >=1.10.0 <1.26.0 | 1.26.0 |

## Am I affected by CVE-2026-25536?

You are affected if you run @modelcontextprotocol/sdk >=1.10.0 <1.26.0. Versions 1.26.0 and later include the fix.

## How do I fix CVE-2026-25536?

Upgrade @modelcontextprotocol/sdk to 1.26.0+. If upgrading is not immediate, deploy one McpServer instance per HTTP client (no shared instances). Audit MCP server logs for cross-client response anomalies.

## How do I find every machine running @modelcontextprotocol/sdk?

Anomity inventories the AI agents, MCP servers, IDE extensions and skills on each developer device, so you can see which machines run @modelcontextprotocol/sdk and which version, then enforce a policy on it.

## References

- cve: https://nvd.nist.gov/vuln/detail/CVE-2026-25536

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Source: Anomity Security Database (https://catalog.anomity.ai/vuln). Detect affected AI tools on developer devices: https://anomity.ai/?utm_source=catalog&utm_medium=vuln-md&utm_campaign=cve-2026-25536