CVE-2001-0033 in Kerberos
Summary
by MITRE
KTH Kerberos IV allows local users to change the configuration of a Kerberos server running at an elevated privilege by specifying an alternate directory using with the KRBCONFDIR environmental variable, which allows the user to gain additional privileges.
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Analysis
by VulDB Data Team • 05/29/2018
The vulnerability described in CVE-2001-0033 represents a critical privilege escalation flaw within the KTH Kerberos IV implementation that directly impacts the security posture of authentication systems relying on this legacy software. This issue stems from improper handling of environment variables during the Kerberos server configuration process, creating a pathway for local attackers to manipulate the server's operational parameters through deliberate environmental manipulation.
The technical flaw manifests when a local user exploits the KRBCONFDIR environment variable to specify an alternate directory for Kerberos configuration files. This environmental variable, designed to allow administrators to specify custom configuration locations, becomes a vector for privilege escalation when improperly validated or restricted. The vulnerability occurs because the Kerberos server process does not adequately verify the legitimacy or security context of the directory specified through this environment variable, allowing an attacker to point the server toward a directory they control.
This vulnerability operates under the principle of insecure environment variable handling, which aligns with CWE-150 and CWE-151 categories that address improper handling of environment variables and configuration file manipulation. The flaw essentially allows a local user to effectively bypass normal access controls by redirecting the Kerberos server to read configuration files from an alternate location, potentially enabling the execution of malicious configuration data that could grant elevated privileges or alter server behavior.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it can fundamentally compromise the integrity and confidentiality of the Kerberos authentication system. An attacker who successfully exploits this vulnerability can potentially modify server configurations to weaken authentication mechanisms, redirect authentication requests, or even establish backdoor access points within the Kerberos infrastructure. This represents a serious threat to the trust model that Kerberos systems are designed to maintain, as it allows local users to effectively subvert the security controls that protect the authentication server.
The attack vector for this vulnerability is particularly concerning because it requires only local system access, making it accessible to users who may not have direct administrative privileges. This aligns with ATT&CK technique T1068 which covers privilege escalation through local system manipulation. The exploitation process involves setting the KRBCONFDIR environment variable to point to a directory controlled by the attacker, then launching the Kerberos server process which will read configuration files from the attacker-controlled location, potentially executing malicious code or injecting unauthorized configuration parameters.
Mitigation strategies for CVE-2001-0033 should focus on implementing proper environment variable validation and restricting the ability of local users to manipulate critical server configuration parameters. System administrators should ensure that the KRBCONFDIR environment variable is properly validated and that the Kerberos server process runs with minimal required privileges. Additionally, implementing proper file system permissions and access controls around Kerberos configuration directories can prevent unauthorized modification of critical server parameters. The most effective long-term solution involves migrating to more modern authentication systems that have addressed these legacy vulnerabilities, as KTH Kerberos IV is an outdated implementation that lacks many of the security controls present in contemporary authentication frameworks.