Is CVE-2025-66414 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2025-66414 being exploited in the wild.

How severe is CVE-2025-66414?

High severity, with a CVSS score of 8.1, published 2 December 2025.

Which products and versions are affected?

@modelcontextprotocol/sdk (npm) SEMVER:introduced=0,fixed=1.24.0.

Is there a fix for CVE-2025-66414?

Yes. @modelcontextprotocol/sdk (npm): upgrade to 1.24.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2025-66414 attacked?

It is attacked over the network.

Am I affected by CVE-2025-66414?

Check whether you run Lfprojects Mcp Typescript Sdk or @modelcontextprotocol/sdk (npm) 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.

CVE-2025-66414: Anthropic MCP TypeScript SDK DNS rebinding bypass on localhost

CVE-2025-66414 · Severity: high · CVSS 8.1 · Published 2025-12-02

The Model Context Protocol (MCP) TypeScript SDK is a development library for building AI assistant integrations. When running HTTP-based MCP servers locally without authentication, the SDK did not enable DNS rebinding protection by default, allowing a malicious website to bypass browser security restrictions and send unauthorized requests to the local server. An attacker could invoke tools or access sensitive resources exposed by the MCP server running on a user's machine.

Technologies: Lfprojects Mcp Typescript Sdk, @modelcontextprotocol/sdk (npm). Vendors: Lfprojects, npm.

Quick answers

Is CVE-2025-66414 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2025-66414 being exploited in the wild.
How severe is CVE-2025-66414?: High severity, with a CVSS score of 8.1, published 2 December 2025.
Which products and versions are affected?: @modelcontextprotocol/sdk (npm) SEMVER:introduced=0,fixed=1.24.0.
Is there a fix for CVE-2025-66414?: Yes. @modelcontextprotocol/sdk (npm): upgrade to 1.24.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2025-66414 attacked?: It is attacked over the network.
Am I affected by CVE-2025-66414?: Check whether you run Lfprojects Mcp Typescript Sdk or @modelcontextprotocol/sdk (npm) 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 1.24.0 or later
```
npm install @modelcontextprotocol/sdk@1.24.0
```

Technical details

The vulnerability is a DNS rebinding bypass (CWE-1188, CWE-350) in the MCP TypeScript SDK's HTTP-based server transports (StreamableHTTPServerTransport and SSEServerTransport). When an unauthenticated HTTP server binds to localhost without explicit enableDnsRebindingProtection, an attacker can craft a malicious website that performs DNS rebinding to redirect legitimate-looking requests to the victim's local MCP server, bypassing same-origin policy (SOP) protections. The attack requires user interaction (visiting a malicious site) and specific deployment conditions (HTTP without auth on localhost). Version 1.24.0 and later enable DNS rebinding protection by default for createMcpExpressApp() and provide hostHeaderValidation() middleware for custom Express configurations. Stdio-based servers are unaffected.

Affected products

Anthropic MCP TypeScript SDK < 1.24.0

Identifiers

CVE-2025-66414
GHSA-w48q-cv73-mx4w

Timeline

2025-12-02: disclosed
2025-12-02: patched: Version 1.24.0 released with DNS rebinding protection enabled by default

References

https://github.com/modelcontextprotocol/typescript-sdk/security/advisories/GHSA-w48q-cv73-mx4w

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