Nagios XI versions prior to 2024R1.2.2 contain a host header injection vulnerability. The application trusts the user-supplied HTTP Host header when constructing absolute URLs without sufficient validation. An unauthenticated, remote attacker can supply a crafted Host header to poison generated links or responses, which may facilitate phishing of credentials, account recovery link hijacking, and web cache poisoning.
The product does not properly verify that the source of data or communication is valid.