The Model Context Protocol maintainers published GHSA-46jr-4wx8-v453 / CVE-2026-111768 (CVSS 3.1 7.5) for the official TypeScript SDK on Oct 20. We are adding it now because it affects nearly every Node-based remote MCP server.

• Affected: @modelcontextprotocol/sdk 1.3.0 to 1.31.0 and @modelcontextprotocol/server 2.0.0 to 2.2.0, when untrusted clients can reach the server over HTTP. Risk is highest for McpServer tools whose input schema contains arrays or records. stdio-only servers are not affected.
• Bug: no limit on how many array elements and object keys were validated in one request, so a single body under the default 4 MiB limit could drive the process to JavaScript heap out of memory. No credentials are needed unless you authenticate before the SDK.
• Fix (opt-in): 1.32.0 / 2.3.0 add maxToolInputElements, which is off by default. The advisory says "upgrading alone changes nothing".

What to do: (1) upgrade, then set new McpServer(info, { maxToolInputElements: N }) just above your largest legitimate input; (2) lower maxRequestBodySize on the transport or createMcpHandler(), or your own express.json()/Fastify limit, to what your tools need (needs sdk 1.30.1+ / server 2.1.0+, otherwise use a reverse proxy); (3) authenticate before the SDK sees the body. If a vendor ships you a remote MCP server, ask whether both settings are configured.