DNS rebinding is an attack technique that abuses changing DNS answers to make a victim’s browser talk to an internal or local service. The attacker first controls a domain that the browser is allowed to load, then changes the domain’s DNS response so the same name points to a different IP address. If the application trusts the hostname too much, the browser may keep using the attacker’s domain while the connection is redirected to a private target on the victim’s network.
This matters because browsers enforce origin rules, but many internal tools also rely on weak host checks, loose CORS settings, or open HTTP APIs. DNS rebinding can turn a harmless-looking web page into a relay for scanning internal services, reading responses, or sending commands to admin panels and automation endpoints. Defenses include validating the real client and target, binding access to authentication instead of hostnames alone, restricting exposure to trusted networks, and using protections such as strong origin checks, CSRF defenses, and DNS-aware allowlists.