MCP TypeScript SDK: One HTTP request within the default size limit could exhaust server memory during validation
Summary
In 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.
No credentials are needed, unless you authenticate requests before they reach the SDK.
Am I affected?
Yes, 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.
Affected versions:
@modelcontextprotocol/sdk1.3.0 through 1.31.0@modelcontextprotocol/server2.0.0 through 2.2.0
What to do
Fix
Upgrade to:
- 1.x:
@modelcontextprotocol/sdk1.32.0 or later - 2.x:
@modelcontextprotocol/server2.3.0 or later
Upgrading alone changes nothing. The patched versions add an McpServer option, maxToolInputElements, that is off by default. Make both of these changes:
- Set
maxToolInputElementsjust above the largest input your tools need, for examplenew McpServer(info, { maxToolInputElements: 10_000 }). It counts array elements and object keys in a call's arguments. A call over the limit gets anisError: trueresult. - Lower the request size limit to what your tools need. The option covers tool arguments only, and the size limit covers everything else. Set
maxRequestBodySizeon the transport orcreateMcpHandler(). If you parse the body yourself, for example withexpress.json()or Fastify, set that parser's limit.
If 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.
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | @modelcontextprotocol/sdk | >= 1.3.0, < 1.32.0 | 1.32.0 |
| npm package | @modelcontextprotocol/server | >= 2.0.0, < 2.3.0 | 2.3.0 |
References
- https://github.com/modelcontextprotocol/typescript-sdk/security/advisories/GHSA-46jr-4wx8-v453
- https://github.com/modelcontextprotocol/typescript-sdk/pull/2926
- https://github.com/modelcontextprotocol/typescript-sdk/pull/2927
- https://github.com/modelcontextprotocol/typescript-sdk/commit/6d8dbc6cb590edf766fcb66b636ca6b654e99c37
- https://github.com/modelcontextprotocol/typescript-sdk/commit/fd26801b3b387742fe24a90ed4b275dd6072209f
- https://github.com/modelcontextprotocol/typescript-sdk
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H- Weakness (CWE)
CWE-770- Platform
- npm
- Package
@modelcontextprotocol/sdk, @modelcontextprotocol/server- Disclosed
- 20.10.2026
- Updated
- 20.10.2026 23:21
Sources and licenses · Edited or translated by DockRay; source rights and applicable licenses are retained.
OSV / GitHub Advisory Database - GHSA-46jr-4wx8-v453 - CC BY 4.0
Vulnerability history: @modelcontextprotocol/server
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 3
- First → latest
- 10.2026 10.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 2
- Medium 1
Disclosures per year
- 2026: 3
-
MCP TypeScript SDK: One HTTP request within the default size limit could exhaust server memory during validation this entry
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