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Name three more reserved ranges in the MCP endpoint blocklist #112

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Name three more reserved ranges in the MCP endpoint blocklist #112

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10 changes: 7 additions & 3 deletions packages/mcp-shared/__tests__/endpoint.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -27,8 +27,10 @@ describe("validateCustomEndpoint", () => {
for (const host of [
"localhost", "app.localhost", "127.0.0.1", "0.0.0.0", "10.1.2.3", "192.168.0.5", "172.16.9.9",
"169.254.169.254", "metadata.google.internal", "thing.internal",
// IPv6 loopback and unique-local, which a URL renders bracketed.
"[::1]", "[fd00::1]", "[fc00::1]",
// Carrier-grade NAT, which some networks route to infrastructure of their own.
"100.64.0.1", "100.127.255.254",
// IPv6 loopback, unspecified, unique-local and link-local, which a URL renders bracketed.
"[::1]", "[::]", "[fd00::1]", "[fc00::1]", "[fe80::1]", "[febf::1]",
]) {
expect(validateCustomEndpoint(env(), `https://${host}/mcp`).ok, host).toBe(false);
}
Expand All @@ -43,7 +45,9 @@ describe("validateCustomEndpoint", () => {
});

it("does not mistake ordinary hosts for encoded addresses", () => {
for (const host of ["mcp.example.com", "8x8.com", "0x.example.com", "mcp.internal.example.com"]) {
for (const host of ["mcp.example.com", "8x8.com", "0x.example.com", "mcp.internal.example.com",
// Addresses outside the ranges above, which must still be accepted.
"100.63.0.1", "100.128.0.1", "[2606:4700::1111]"]) {
expect(isBlockedHost(host), host).toBe(false);
}
});
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3 changes: 3 additions & 0 deletions packages/mcp-shared/src/endpoint.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -23,8 +23,11 @@ const BLOCKED_HOST_PATTERNS = [
/^192\.168\./,
/^172\.(1[6-9]|2[0-9]|3[01])\./,
/^169\.254\./,
/^100\.(6[4-9]|[7-9][0-9]|1[01][0-9]|12[0-7])\./,
/^\[?::1\]?$/,
/^\[?::\]?$/,
/^\[?f[cd][0-9a-f]{2}:/i,
/^\[?fe[89ab][0-9a-f]:/i,
/^metadata\./i,
/\.internal$/i,
];
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