CVE-2026-111768: MCP TypeScript SDK memory exhaustion via unbounded validation

CVE-2026-111768 · Severity: high · CVSS 7.5 · Published 2026-11-05

The MCP TypeScript SDK, used to build servers that provide tools and resources to AI models, fails to limit validation of input arrays and object keys. An attacker can send a single HTTP request within the normal size limit that contains deeply nested or massively repeated data, causing the server to run out of memory and crash, disrupting service for legitimate users.

Technologies: Anthropic @Modelcontextprotocol/Sdk, @modelcontextprotocol/sdk (npm), @modelcontextprotocol/server (npm). Vendors: Anthropic, npm.

Quick answers

Is CVE-2026-111768 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-111768 being exploited in the wild.
How severe is CVE-2026-111768?
High severity, with a CVSS score of 7.5, published 5 November 2026.
Which products and versions are affected?
Anthropic @Modelcontextprotocol/Sdk 1.3.0 through 1.31.0; Anthropic @Modelcontextprotocol/Server 2.0.0 through 2.2.0; @modelcontextprotocol/sdk (npm) >= 1.3.0, < 1.32.0, SEMVER:introduced=1.3.0,fixed=1.32.0; @modelcontextprotocol/server (npm) >= 2.0.0, < 2.3.0, SEMVER:introduced=2.0.0,fixed=2.3.0.
Is there a fix for CVE-2026-111768?
Yes. @modelcontextprotocol/sdk (npm): upgrade to 1.32.0 or later; @modelcontextprotocol/server (npm): upgrade to 2.3.0 or later. Until then: Set the new `maxToolInputElements` option to a reasonable limit just above your largest expected input (e.g., `new McpServer(info, { maxToolInputElements: 10_000 })`), and lower the request size limit via `maxRequestBodySize` on the transport or parser to the minimum your tools require. If upgrading is not yet possible, reducing `maxRequestBodySize` alone will help; versions 1.30.1 and 2.1.0+ support this option. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-111768 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-111768?
Check whether you run Anthropic @Modelcontextprotocol/Sdk, Anthropic @Modelcontextprotocol/Server, @modelcontextprotocol/sdk (npm) or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • @modelcontextprotocol/sdk (npm): upgrade to 1.32.0 or later
    npm install @modelcontextprotocol/sdk@1.32.0
  • @modelcontextprotocol/server (npm): upgrade to 2.3.0 or later
    npm install @modelcontextprotocol/server@2.3.0

Set the new `maxToolInputElements` option to a reasonable limit just above your largest expected input (e.g., `new McpServer(info, { maxToolInputElements: 10_000 })`), and lower the request size limit via `maxRequestBodySize` on the transport or parser to the minimum your tools require. If upgrading is not yet possible, reducing `maxRequestBodySize` alone will help; versions 1.30.1 and 2.1.0+ support this option.

Technical details

The vulnerability is a resource exhaustion flaw in request validation: servers accept unbounded numbers of array elements and object keys during validation, allowing a single HTTP request under the 4 MiB default size limit to consume arbitrary memory and trigger a JavaScript heap out-of-memory abort. The attack requires network access to an HTTP-exposed McpServer with tools that accept arrays or records as input; stdio-only servers are not vulnerable. The advisory provides two mitigations: setting the new `maxToolInputElements` option and lowering `maxRequestBodySize` to the minimum needed.

Affected products

  • Anthropic @modelcontextprotocol/sdk 1.3.0 through 1.31.0
  • Anthropic @modelcontextprotocol/server 2.0.0 through 2.2.0

Identifiers

  • CVE-2026-111768
  • GHSA-46jr-4wx8-v453

Timeline

  • 2026-10-20: disclosed

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