DNS rebinding :* allowlist matches Host/Origin suffixes that are not ports

What happened

TransportSecurityMiddleware treats allowed_hosts / allowed_origins entries that end in :* as a prefix match: value.startswith(base + ":").

With allowed_hosts=["127.0.0.1:*"] or ["wild.example:*"], these Host values are accepted today:

• 127.0.0.1:8080.evil
• wild.example:9000.evil

The same pattern accepts Origin http://wild.example:9000.evil for http://wild.example:*.

Existing tests only cover a numeric port (wild.example:9000). They do not cover a suffix after the port.

What I expected

base:* should mean base plus a numeric port, not any string that starts with base:.

How to reproduce

On main @ 08a3bc8:

from mcp.server.transport_security import TransportSecurityMiddleware, TransportSecuritySettings
from starlette.requests import Request

settings = TransportSecuritySettings(
    enable_dns_rebinding_protection=True,
    allowed_hosts=["wild.example:*"],
    allowed_origins=["http://wild.example:*"],
)
mw = TransportSecurityMiddleware(settings)
req = Request({"type": "http", "method": "GET", "headers": [(b"host", b"wild.example:9000.evil")]})
# validate_request returns None (accept). I expected 421.

I can send a PR that requires the suffix after base: to be digits, plus tests for the suffix cases. Happy to do that if you want it.

Written with AI assistance. I read the matcher next to tests/server/test_transport_security.py and reproduced it locally.

從 mcp/server/transport_security.py 開始，其中 TransportSecurityMiddleware 會比對 allowed_hosts 和 allowed_origins，接著閱讀 tests/server/test_transport_security.py。重現回報的後綴案例，並將其與現有的數字連接埠涵蓋範圍進行比較。完成的標準是數字連接埠仍然會被接受，而像 wild.example:9000.evil 這樣的值以及相符的 Origin 會被拒絕。