Executive Summary

This vulnerability is a flaw in the util-linux package, specifically in the login(1) utility when used with the -h option. The issue is improper hostname canonicalization, meaning the supplied remote hostname can be altered before it is set as PAM_RHOST.

A remote attacker can exploit this by providing a specially crafted hostname, which may bypass host-based Pluggable Authentication Modules (PAM) access control rules that depend on fully qualified domain names.

This flaw can lead to unauthorized access because the hostname used for authentication checks can be manipulated.

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Impact Analysis

The vulnerability can allow a remote attacker to bypass host-based PAM access control rules by manipulating the hostname used during login authentication.

This could result in unauthorized access to systems that rely on hostname-based authentication controls, potentially compromising system security.

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Compliance Impact

This vulnerability allows an attacker to bypass host-based PAM access control rules, potentially leading to unauthorized remote logins.

Such unauthorized access could impact compliance with standards and regulations like GDPR and HIPAA, which require strict access controls to protect sensitive data.

However, the provided information does not explicitly discuss the direct effects on compliance with these regulations.

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Detection Guidance

This vulnerability involves the login(1) utility in util-linux when invoked with the -h option, which affects hostname canonicalization and PAM_RHOST setting.

To detect if your system is vulnerable, you should check if your system uses the login(1) utility with the -h option in remote login methods such as telnet or rlogin daemons, or custom wrappers.

Additionally, verify if your PAM configuration uses host-based access control modules like pam_access that rely on PAM_RHOST and differentiate between fully qualified domain names (FQDNs) and short hostnames.

You can check for the presence of the util-linux package and its version to determine if it includes the vulnerable login utility.

• Check util-linux package version: `rpm -q util-linux` (on RPM-based systems) or `dpkg -s util-linux` (on Debian-based systems).
• Inspect PAM configuration files for pam_access usage: `grep pam_access /etc/pam.d/*`.
• Check if login(1) is invoked with the -h option in remote login services or wrappers by reviewing service configurations or scripts.

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Mitigation Strategies

Immediate mitigation steps include preventing the exploitation of the hostname canonicalization flaw in the login(1) utility.

• Avoid using remote login methods that invoke login(1) with the -h option, such as telnet or rlogin daemons, until a patch is applied.
• Review and tighten PAM access control rules, especially those relying on PAM_RHOST and hostname canonicalization, to reduce reliance on hostname-based access control.
• Apply any available patches or updates to the util-linux package that address this vulnerability.
• Consider disabling or restricting remote login services that use vulnerable login(1) invocations.

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