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Fencer Vulns
high 7.5

GHSA-f897-62hf-6gxq json

MCP TypeScript SDK: HTTP server transports and handlers did not limit request body size or JSON-RPC batch length

published 2026-10-27 12 d ago modified 2026-10-27 12 d ago

cvss
7.5
version 3.1, GitHub
cisa kev
Not listed
not in CISA's catalog
epss
—
no score, EPSS covers CVEs only
public exploits
0
none known

Summary

### Summary In affected versions, MCP servers reachable over HTTP put no limit on the size of a POST body or on the number of messages in a JSON-RPC batch. Large requests could exhaust the server's memory, and one long batch could block it from serving anyone else. No credentials were needed, unless your application authenticates requests before they reach the SDK.

### Am I affected? Yes, if clients you do not fully trust can reach your server over Streamable HTTP. A body parser such as `express.json()` does not protect you, because it does not limit batch length. Servers that only use stdio are not affected.

Affected versions:

- `@modelcontextprotocol/sdk` 1.10.0 through 1.30.0 - `@modelcontextprotocol/server` 2.0.0 - `@modelcontextprotocol/node` 2.0.0 - `@modelcontextprotocol/hono` 2.0.0

### Fix Upgrade to:

- 1.x: `@modelcontextprotocol/sdk` 1.30.1 or later - 2.x: `@modelcontextprotocol/server` 2.1.0, `@modelcontextprotocol/node` 2.1.0 and `@modelcontextprotocol/hono` 2.0.1 or later. Upgrade every one you have installed.

Bodies over 4 MiB now get `413`, and batches over 100 messages get `400`. If your clients send larger bodies, raise the new `maxRequestBodySize` option.

If you cannot upgrade yet, cap request body size in a reverse proxy.

Patch / fix

  • npm @modelcontextprotocol/sdk 1.30.1
  • npm @modelcontextprotocol/server 2.1.0
  • npm @modelcontextprotocol/node 2.1.0
  • npm @modelcontextprotocol/hono 2.0.1

CVSS scores

assigned by version score vector
GitHub 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
npm @modelcontextprotocol/sdk
>=1.10.0, <1.30.1
1.30.1
npm @modelcontextprotocol/server
>=2.0.0, <2.1.0
2.1.0
npm @modelcontextprotocol/node
>=2.0.0, <2.1.0
2.1.0
npm @modelcontextprotocol/hono
>=2.0.0, <2.0.1
2.0.1

Classification

Weakness
  • CWE-770 Allocation of Resources Without Limits or Throttling

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.