fix(mcp): skip loopback and IPv6 private IPs in getClientIp#2875
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fahreddinozcan merged 2 commits intoJul 6, 2026
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Extract getClientIp into lib/client-ip.ts and extend the private/local IP filter to cover 127.0.0.0/8, 169.254.0.0/16, ::1, fe80::/10, and fc00::/7 when walking X-Forwarded-For. Proxies that prepend loopback or health-check addresses no longer pollute mcp-client-ip analytics. Fixes upstash#2874
Anchor the fe80::/10 and fc00::/7 regexes to full 4-digit first hextets so abbreviated hextets like fe8::1 or fc::1 are no longer misclassified as private. Match IPv6 loopback in any textual form (0::1, 0:0:0:0:0:0:0:1), add CGNAT (100.64.0.0/10) to the skip list, and add a patch changeset.
fahreddinozcan
approved these changes
Jul 6, 2026
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Summary
Extend
getClientIpprivate/local IP filtering so reverse proxies that prepend loopback or health-check addresses no longer pollutemcp-client-ipanalytics.Fixes #2874
Motivation
getClientIpalready skipped RFC1918 ranges when walkingX-Forwarded-For, but still accepted loopback (127.*), IPv4 link-local (169.254.*), and common IPv6 private ranges. A header like127.0.0.1, 8.8.8.8incorrectly returned127.0.0.1instead of the public client IP.Changes
getClientIpintopackages/mcp/src/lib/client-ip.tsisPrivateOrLocalIp()covering RFC1918,127.0.0.0/8,169.254.0.0/16,::1,fe80::/10, andfc00::/7index.tswithout changing fallback behavior when all forwarded IPs are privatepackages/mcp/test/client-ip.test.tsTests
cd packages/mcp npx vitest run npx tsc --noEmit npx eslint src/lib/client-ip.ts src/index.ts test/client-ip.test.tsNotes
remoteAddresshandling is unchanged (noX-Forwarded-Forpath)