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VulnerabilityPublished

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

Affects @modelcontextprotocol/sdkSource GCVE Database

0

CVSS 7.5 High : upgrade to 1.30.1 soon.

Data as of 27 Oct 2026, 20:29 UTC

CVSS 3.1 base score
7.5High
How severe the flaw is on the 0–10 CVSS scale.
Patch
Available – fixed in 1.30.1, 2.1.0, 2.0.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

What to do

Upgrade @modelcontextprotocol/sdk to 1.30.1; @modelcontextprotocol/server and @modelcontextprotocol/node to 2.1.0; @modelcontextprotocol/hono to 2.0.1.

Affected software

ProductAffectedFixed in
npm@modelcontextprotocol/sdkAffected
  • >=1.10.0 <1.30.1
Fixed in
  • 1.30.1
npm@modelcontextprotocol/serverAffected
  • >=2.0.0 <2.1.0
Fixed in
  • 2.1.0
npm@modelcontextprotocol/nodeAffected
  • >=2.0.0 <2.1.0
Fixed in
  • 2.1.0
npm@modelcontextprotocol/honoAffected
  • >=2.0.0 <2.0.1
Fixed in
  • 2.0.1

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade all affected MCP packages to the fixed versions: @modelcontextprotocol/sdk to 1.30.1 or later, @modelcontextprotocol/server and @modelcontextprotocol/node to 2.1.0 or later, and @modelcontextprotocol/hono to 2.0.1 or later. These versions enforce a 4 MiB maximum request body size and a maximum of 100 messages per JSON-RPC batch. If upgrading is not immediately possible, implement request body size limits in a reverse proxy in front of the server to prevent large requests from reaching the application.

Description

Certain versions of the MCP TypeScript SDK and related packages do not limit HTTP POST request body size or JSON-RPC batch length. This allows an attacker to send very large requests or long batches, potentially exhausting server memory and causing denial of service. No authentication is required unless implemented outside the SDK. Fixed versions impose limits on request size and batch length.

References

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