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Response snapshot Oct 27, 2026, 20:26 UTC

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VulnerabilityGHSA-f897-62hf-6gxq

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

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.

At a glance

Exploited
Not known
Severity
Not scored yet
Chance of exploitation
Not estimated
Sources
1 source

What to do

GitHub lists first patched versions: @modelcontextprotocol/sdk: 1.30.1; @modelcontextprotocol/server: 2.1.0; @modelcontextprotocol/node: 2.1.0; @modelcontextprotocol/hono: 2.0.1. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-f897-62hf-6gxq (opens a new tab)

What happened

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.

Continue reading

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.

Affected package ranges reported by GitHub: @modelcontextprotocol/sdk: >= 1.10.0, < 1.30.1 @modelcontextprotocol/server: >= 2.0.0, < 2.1.0 @modelcontextprotocol/node: >= 2.0.0, < 2.1.0 @modelcontextprotocol/hono: >= 2.0.0, < 2.0.1

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-f897-62hf-6gxq (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-f897-62hf-6gxq, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 27). MCP TypeScript SDK: HTTP server transports and handlers did not limit request body size or JSON-RPC batch length. https://kevwire.com/record/GHSA-f897-62hf-6gxq

MLA

"MCP TypeScript SDK: HTTP server transports and handlers did not limit request body size or JSON-RPC batch length." KEVWire, 27 Oct. 2026, kevwire.com/record/GHSA-f897-62hf-6gxq.

Chicago

KEVWire. "MCP TypeScript SDK: HTTP server transports and handlers did not limit request body size or JSON-RPC batch length." Last modified October 27, 2026. https://kevwire.com/record/GHSA-f897-62hf-6gxq.

Evidence summary (plain text)

MCP TypeScript SDK: HTTP server transports and handlers did not limit request body size or JSON-RPC batch length (Oct 27, 2026).
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.

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.
Sources:
GitHub-reviewed advisory GHSA-f897-62hf-6gxq: https://github.com/advisories/GHSA-f897-62hf-6gxq
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc
Record ID: GHSA-f897-62hf-6gxq.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 27, 2026, 20:25 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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