CVE-2025-66414: @modelcontextprotocol/sdk Model Context Protocol (MCP) TypeScript Vulnerability

HIGH
Advisory Identifier: GHSA-w48q-cv73-mx4w
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CWE-1188 CWE-350
Published
Advisory Summary

CVE-2025-66414 is a HIGH model context protocol (mcp) typescript vulnerability (CWE-1188: Initialization of a Resource with an Insecure Default) affecting @modelcontextprotocol/sdk libraries in the npm ecosystem. The issue involves model context protocol (mcp) typescript sdk does not enable dns rebinding protection by default. Remediation is available by upgrading affected packages to version 1.24.0.

CVE-2025-66414 at a Glance

CVE Identifier CVE-2025-66414
GHSA Identifier GHSA-w48q-cv73-mx4w
Severity HIGH
CVSS v3.1 Base Score N/A
CWE Classification CWE-1188: Initialization of a Resource with an Insecure Default
Affected Product @modelcontextprotocol/sdk
Package Ecosystem npm
Published Date
Last Updated

How to Fix CVE-2025-66414

To remediate this vulnerability, upgrade all affected @modelcontextprotocol/sdk dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

@modelcontextprotocol/sdk fixed: 1.24.0 
npm install @modelcontextprotocol/sdk@1.24.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls @modelcontextprotocol/sdk

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2025-66414, inspect your project dependencies using npm:

npm ls @modelcontextprotocol/sdk

Analyze the terminal output to locate any version of @modelcontextprotocol/sdk in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.24.0), your application is affected.

Note: The npm ls @modelcontextprotocol/sdk command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-1188: Initialization of a Resource with an Insecure Default, where the product initializes or sets a resource with a default that is intended to be changed by the product's installer, administrator, or maintainer, but the default is not secure. In @modelcontextprotocol/sdk, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

The Model Context Protocol (MCP) TypeScript SDK does not enable DNS rebinding protection by default for HTTP-based servers. When an HTTP-based MCP server is run on localhost without authentication with `StreamableHTTPServerTransport` or `SSEServerTransport` and has not enabled `enableDnsRebindingProtection`, a malicious website could exploit DNS rebinding to bypass same-origin policy restrictions and send requests to the local MCP server. This could allow an attacker to invoke tools or access resources exposed by the MCP server on behalf of the user in those limited circumstances. Note that running HTTP-based MCP servers locally without authentication is not recommended per MCP security best practices. This issue does not affect servers using stdio transport. Servers created via `createMcpExpressApp()` now have this protection enabled by default when binding to localhost. Users with custom Express configurations are advised to update to version `1.24.0` and apply the exported `hostHeaderValidation()` middleware when running an unauthenticated server on localhost.

CVE-2025-66414 Affected @modelcontextprotocol/sdk Versions

1 component(s)
Fixed Versions:
1.24.0
Product / Package Ecosystem Affected Versions Fixed Version
@modelcontextprotocol/sdk
npm/@modelcontextprotocol/sdk
npm
< 1.24.0
1.24.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/modelcontextprotocol/typescript-sdk/security/advisories/GHSA-w48q-cv73-mx4w
NVD — CVE-2025-66414 NVD
https://nvd.nist.gov/vuln/detail/CVE-2025-66414
@modelcontextprotocol/sdk Source Repository REPOSITORY
https://github.com/modelcontextprotocol/typescript-sdk/pull/1205
Security Fix Commit FIX COMMIT
https://github.com/modelcontextprotocol/typescript-sdk/commit/09623e2aa5044f9e9da62c73d820a8250b9d97ed
Security Fix Commit FIX COMMIT
https://github.com/modelcontextprotocol/typescript-sdk/commit/608360047dc6899f1cf4f0226eb62fe7b11b3898
@modelcontextprotocol/sdk Source Repository REPOSITORY
https://github.com/modelcontextprotocol/typescript-sdk

Frequently Asked Questions

What is CVE-2025-66414?
CVE-2025-66414 is a security vulnerability in @modelcontextprotocol/sdk involving Model Context Protocol (MCP) TypeScript SDK does not enable DNS rebinding protection by default under CWE-1188: Initialization of a Resource with an Insecure Default.
Which @modelcontextprotocol/sdk versions are affected?
Affected versions include releases prior to 1.24.0 across affected packages: @modelcontextprotocol/sdk.
What version fixes CVE-2025-66414?
Upgrading to 1.24.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is @modelcontextprotocol/sdk affected?
Yes, @modelcontextprotocol/sdk is affected in releases prior to 1.24.0. Upgrade your dependency to 1.24.0 or later.
What CWE is associated with CVE-2025-66414?
CVE-2025-66414 is classified under CWE-1188: Initialization of a Resource with an Insecure Default (The product initializes or sets a resource with a default that is intended to be changed by the product's installer, administrator, or maintainer, but the default is not secure.).
How can I check npm dependencies for CVE-2025-66414?
Run the dependency tree command: 'npm ls @modelcontextprotocol/sdk'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-w48q-cv73-mx4w",
  "modified" : "2025-12-02T21:43:49Z",
  "published" : "2025-12-02T16:51:57Z",
  "aliases" : [ "CVE-2025-66414" ],
  "summary" : "Model Context Protocol (MCP) TypeScript SDK does not enable DNS rebinding protection by default",
  "details" : "The Model Context Protocol (MCP) TypeScript SDK does not enable DNS rebinding protection by default for HTTP-based servers. When an HTTP-based MCP server is run on localhost without authentication with `StreamableHTTPServerTransport` or `SSEServerTransport` and has not enabled `enableDnsRebindingProtection`, a malicious website could exploit DNS rebinding to bypass same-origin policy restrictions and send requests to the local MCP server. This could allow an attacker to invoke tools or access resources exposed by the MCP server on behalf of the user in those limited circumstances.\n\nNote that running HTTP-based MCP servers locally without authentication is not recommended per MCP security best practices. This issue does not affect servers using stdio transport.\n\nServers created via `createMcpExpressApp()` now have this protection enabled by default when binding to localhost. Users with custom Express configurations are advised to update to version `1.24.0` and apply the exported `hostHeaderValidation()` middleware when running an unauthenticated server on localhost.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "@modelcontextprotocol/sdk"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.24.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/modelcontextprotocol/typescript-sdk/security/advisories/GHSA-w48q-cv73-mx4w"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2025-66414"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/modelcontextprotocol/typescript-sdk/pull/1205"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/modelcontextprotocol/typescript-sdk/commit/09623e2aa5044f9e9da62c73d820a8250b9d97ed"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/modelcontextprotocol/typescript-sdk/commit/608360047dc6899f1cf4f0226eb62fe7b11b3898"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/modelcontextprotocol/typescript-sdk"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1188", "CWE-350" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2025-12-02T16:51:57Z",
    "nvd_published_at" : "2025-12-02T19:15:52Z"
  }
}