CVE-2025-66414: MCP TypeScript SDK did not enable DNS rebinding protection by default
- Product
- @modelcontextprotocol/sdk (npm)
- CVE
- CVE-2025-66414
- Affected
- < 1.24.0
- Fixed in
- 1.24.0
Last verified against sources: October 16, 2026
What happened
- According to GitHub Advisory Database's advisory (Dec 2, 2025), HTTP-based MCP servers run on localhost without authentication, and without enableDnsRebindingProtection, could be reached by a malicious website through DNS rebinding. [1]
Impact
- An attacker could invoke tools or access resources exposed by the local MCP server on the user's behalf. Servers using stdio are not affected. [1]
What was done
- In 1.24.0, servers created via createMcpExpressApp() enable the protection by default when binding to localhost. [1]
How to protect yourself
- Update to 1.24.0; with a custom Express setup, apply hostHeaderValidation() middleware, and avoid unauthenticated local HTTP servers. [1]
Sources
- GHSA-w48q-cv73-mx4w — GitHub Advisory Database
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