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CVE

CVE-2025-66414

Model Context Protocol (MCP) TypeScript SDK does not enable DNS rebinding protection by default
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CVE

CVE-2025-66414

Model Context Protocol (MCP) TypeScript SDK does not enable DNS rebinding protection by default

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.

Package Versions Affected

Package Version
patch Availability
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CVSS Version

Severity
Base Score
CVSS Version
Score Vector
C
H
U
7.6
-
4.0
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
C
H
U
0
-
C
H
U
8.1
-
3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N

Related Resources

No items found.

References

https://github.com/modelcontextprotocol/typescript-sdk/security/advisories/GHSA-w48q-cv73-mx4w, https://nvd.nist.gov/vuln/detail/CVE-2025-66414, https://github.com/modelcontextprotocol/typescript-sdk/pull/1205, https://github.com/modelcontextprotocol/typescript-sdk/commit/09623e2aa5044f9e9da62c73d820a8250b9d97ed, https://github.com/modelcontextprotocol/typescript-sdk/commit/608360047dc6899f1cf4f0226eb62fe7b11b3898, https://github.com/modelcontextprotocol/typescript-sdk

Severity

8.1

CVSS Score
0
10

Basic Information

Ecosystem
Base CVSS
8.1
EPSS Probability
0.00035%
EPSS Percentile
0.09895%
Introduced Version
0,1.13.3
Fix Available
1.24.0

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