fix: enable DNS rebinding protection by default for secure-by-default#2275
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Jah-yee wants to merge 2 commits intomodelcontextprotocol:mainfrom
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fix: enable DNS rebinding protection by default for secure-by-default#2275Jah-yee wants to merge 2 commits intomodelcontextprotocol:mainfrom
Jah-yee wants to merge 2 commits intomodelcontextprotocol:mainfrom
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March 12, 2026 01:21
…response Per RFC 6749 Section 6, the authorization server MAY issue a new refresh token in the refresh response. If omitted, the client must preserve the existing one. This fix prevents token refresh failures after the first refresh when using OAuth providers that don't return refresh tokens in responses (e.g., Google, Auth0 without rotation, Okta in persistent token mode). Fixes modelcontextprotocol#2270
Per issue modelcontextprotocol#2269, the current default disables DNS rebinding protection, which makes MCP servers vulnerable to DNS rebinding attacks on local networks. This change switches the default to secure-by-default (enable_dns_rebinding_protection=True), with developers able to explicitly opt-out for backwards compatibility if needed. Reported by @hhhashexe (SkillFence Security)
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Summary
Per issue #2269, the current default disables DNS rebinding protection, which makes MCP servers vulnerable to DNS rebinding attacks on local networks.
This change switches the default to secure-by-default (
enable_dns_rebinding_protection=True), with developers able to explicitly opt-out for backwards compatibility if needed.Changes
enable_dns_rebinding_protectionfromFalsetoTrueinTransportSecurityMiddleware.__init__Security Impact
With this change, developers following official examples and tutorials will have DNS rebinding protection enabled by default. Those who need backwards compatibility can explicitly disable it:
Reported by @hhhashexe (SkillFence Security)