CVE-2025-66414 DNS Rebinding Protection Disabled by Default in Model Context Protocol TypeScript SDK for Servers Running on Localhost
Attackers can use DNS rebinding to bypass same-origin policy and interact with local MCP servers if protection is disabled and authentication is missing.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2025-66414?
CVE-2025-66414 is a high-severity server-side request forgery vulnerability in modelcontextprotocol typescript-sdk, published on 2 Dec 2025. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
MCP TypeScript SDK is the official TypeScript SDK for Model Context Protocol servers and clients. Prior to 1.24.0, 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. This vulnerability is fixed in 1.24.0.
Weakness: CWE-1188
Which versions are affected by CVE-2025-66414?
2 open source packages ship an affected version, including @modelcontextprotocol/sdk. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
@modelcontextprotocol/sdk npm | All versions | 1.24.0 |
@modelcontextprotocol/sdk npm | All versions | 1.24.0 |
Products include Lfprojects Mcp Typescript Sdk.
How do I fix CVE-2025-66414?
Upgrade @modelcontextprotocol/sdk to 1.24.0 or later.
Upgrade, and send outbound requests through an allow-list that blocks internal addresses. More about Server-side request forgery.
Is CVE-2025-66414 being exploited?
There is no known exploitation of CVE-2025-66414 in the wild and no public exploit code.
Other vulnerabilities in modelcontextprotocol typescript-sdk
Sources
Also known as CLSA-2026-1789632492, CLSA-2026-1790202402, CVE-2025-11249, GHSA-w48q-cv73-mx4w, MINI-j4rv-88g7-gcc5, MINI-jgq7-2mjx-hf2c and 3 more.