{"id":"GHSA-46jr-4wx8-v453","summary":"MCP TypeScript SDK: One HTTP request within the default size limit could exhaust server memory during validation","details":"### Summary\nIn affected versions, servers put no limit on how many array elements and object keys they validated in one request. One HTTP request within the default 4 MiB size limit could exhaust the server's memory, and the process aborted with `JavaScript heap out of memory`.\n\nNo credentials are needed, unless you authenticate requests before they reach the SDK.\n\n### Am I affected?\nYes, if clients you do not fully trust can reach your server over HTTP. The risk is highest for `McpServer` tools whose input contains an array or a record. stdio-only servers are not affected.\n\nAffected versions:\n\n- `@modelcontextprotocol/sdk` 1.3.0 through 1.31.0\n- `@modelcontextprotocol/server` 2.0.0 through 2.2.0\n\n### Fix\nUpgrade to:\n\n- 1.x: `@modelcontextprotocol/sdk` 1.32.0 or later\n- 2.x: `@modelcontextprotocol/server` 2.3.0 or later\n\n**Upgrading alone changes nothing.** The patched versions add an `McpServer` option, `maxToolInputElements`, that is off by default. Make both of these changes:\n\n1. Set `maxToolInputElements` just above the largest input your tools need, for example `new McpServer(info, { maxToolInputElements: 10_000 })`. It counts array elements and object keys in a call's arguments. A call over the limit gets an `isError: true` result.\n2. Lower the request size limit to what your tools need. The option covers tool arguments only, and the size limit covers everything else. Set `maxRequestBodySize` on the transport or `createMcpHandler()`. If you parse the body yourself, for example with `express.json()` or Fastify, set that parser's limit.\n\nIf you cannot upgrade yet, make the second change. `maxRequestBodySize` needs `@modelcontextprotocol/sdk` 1.30.1 or `@modelcontextprotocol/server` 2.1.0. Below that, use a reverse proxy.","aliases":["CVE-2026-111768"],"modified":"2026-10-20T20:15:05.222078887Z","published":"2026-10-20T20:06:35Z","database_specific":{"severity":"HIGH","github_reviewed":true,"github_reviewed_at":"2026-10-20T20:06:35Z","nvd_published_at":null,"cwe_ids":["CWE-770"]},"references":[{"type":"WEB","url":"https://github.com/modelcontextprotocol/typescript-sdk/security/advisories/GHSA-46jr-4wx8-v453"},{"type":"WEB","url":"https://github.com/modelcontextprotocol/typescript-sdk/pull/2926"},{"type":"WEB","url":"https://github.com/modelcontextprotocol/typescript-sdk/pull/2927"},{"type":"WEB","url":"https://github.com/modelcontextprotocol/typescript-sdk/commit/6d8dbc6cb590edf766fcb66b636ca6b654e99c37"},{"type":"WEB","url":"https://github.com/modelcontextprotocol/typescript-sdk/commit/fd26801b3b387742fe24a90ed4b275dd6072209f"},{"type":"PACKAGE","url":"https://github.com/modelcontextprotocol/typescript-sdk"}],"affected":[{"package":{"name":"@modelcontextprotocol/sdk","ecosystem":"npm","purl":"pkg:npm/%40modelcontextprotocol/sdk"},"ranges":[{"type":"SEMVER","events":[{"introduced":"1.3.0"},{"fixed":"1.32.0"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-46jr-4wx8-v453/GHSA-46jr-4wx8-v453.json"}},{"package":{"name":"@modelcontextprotocol/server","ecosystem":"npm","purl":"pkg:npm/%40modelcontextprotocol/server"},"ranges":[{"type":"SEMVER","events":[{"introduced":"2.0.0"},{"fixed":"2.3.0"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-46jr-4wx8-v453/GHSA-46jr-4wx8-v453.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"}]}