MCP TypeScript SDK: One HTTP request within the default size limit could exhaust server memory during validation (CVE-2026-111768)
Description
A vulnerability in the MCP TypeScript SDK and server allows a single HTTP request within the default 4 MiB size limit to exhaust server memory during validation by sending excessive array elements or object keys. This causes the server process to abort with a 'JavaScript heap out of memory' error. No authentication is required unless the server enforces it before the SDK processes requests. The issue affects versions 1.3.0 through 1.31.0 of @modelcontextprotocol/sdk and 2.0.0 through 2.2.0 of @modelcontextprotocol/server. Fixed versions are 1.32.0+ for the SDK and 2.3.0+ for the server, which introduce a new option to limit input elements and recommend lowering request size limits.
CVSS v3.1
Score 7.5high
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The MCP TypeScript SDK and server do not limit the number of array elements and object keys validated in a single HTTP request, allowing a request within the default 4 MiB size limit to exhaust server memory and cause a crash with a 'JavaScript heap out of memory' error. This vulnerability affects @modelcontextprotocol/sdk versions 1.3.0 through 1.31.0 and @modelcontextprotocol/server versions 2.0.0 through 2.2.0. The fix involves upgrading to versions 1.32.0 or later for the SDK and 2.3.0 or later for the server, which add a configurable 'maxToolInputElements' option to limit validated input elements. Additionally, lowering the request size limit is recommended to mitigate the risk. If upgrading is not immediately possible, lowering the request size limit using 'maxRequestBodySize' or a reverse proxy is advised.
Potential Impact
An attacker can send a single HTTP request with a large number of array elements or object keys within the default 4 MiB size limit, causing the server to exhaust its memory and abort the process with a 'JavaScript heap out of memory' error. This results in a denial of service (DoS) condition. No credentials are required to trigger this vulnerability unless the server enforces authentication before SDK processing. The impact is limited to servers that accept untrusted client requests over HTTP and use the affected MCP SDK or server versions.
Mitigation Recommendations
A patch is available. Upgrade to @modelcontextprotocol/sdk version 1.32.0 or later and @modelcontextprotocol/server version 2.3.0 or later. After upgrading, configure the 'maxToolInputElements' option to a value just above the largest expected input size to limit validated elements. Also, reduce the HTTP request size limit using 'maxRequestBodySize' on the transport or handler, or the equivalent in your HTTP parser. If upgrading is not possible immediately, reduce the request size limit using 'maxRequestBodySize' (available in SDK 1.30.1 or server 2.1.0) or use a reverse proxy to limit request sizes.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-46jr-4wx8-v453
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-111768"]
- Ecosystems
- ["npm"]
- Database Specific Severity
- HIGH
- Cvss Version
- 3.1
Threat ID: 6ad7ec462cdf04f6566b9fb0
Added to database: 10/20/2026, 22:33:42 UTC
Last enriched: 10/20/2026, 22:43:14 UTC
Last updated: 10/20/2026, 22:43:14 UTC
Views: 7
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