Summary: Improper hostname canonicalization in util-linux login(1) when invoked with -h can modify the supplied remote hostname before setting PAM_RHOST, potentially allowing bypass of host-based PAM access control rules (e.g., pam_access) that rely on fully qualified domain names. Requirements to exploit: An attacker must be able to access a remote login pathway that invokes login(1) with the -h <remotehost> option (e.g., telnet/rlogin-style daemons or custom wrappers). The target system must use PAM modules relying on PAM_RHOST for authorization decisions (such as pam_access) and have rules that distinguish between FQDNs and short hostnames. The local system hostname must share the same domain suffix as the attacker-supplied hostname.