Spoofable client IP address
Summary: PortSwigger Research describes a spoofable client IP address issue: when an application trusts HTTP request headers such as X-Forwarded-For, True-Client-IP, or X-Real-IP to specify the connecting client's remote IP address, malicious clients can spoof their IP. The research notes this is not necessarily a vulnerability on its own, but some applications use client IP addresses to enforce access controls and rate limits, such as restricting administrative functionality to the server's local IP or limiting failed login attempts per unique IP.
What you should know: If your access controls or login rate limits key off a header like X-Forwarded-For, an attacker sets that header and picks which IP the application sees - walking past the restriction or resetting the failed-login count at will.
Read the original at PortSwigger Research ↗
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