CVE-2001-0093 in FreeBSD
Summary
by MITRE
Vulnerability in telnetd in FreeBSD 1.5 allows local users to gain root privileges by modifying critical environmental variables that affect the behavior of telnetd.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 06/20/2024
The vulnerability identified as CVE-2001-0093 represents a critical privilege escalation flaw within the telnetd service of FreeBSD 1.5 systems. This issue stems from inadequate input validation and environmental variable handling within the telnet daemon implementation, creating a pathway for local attackers to elevate their privileges to the root level. The vulnerability specifically targets the telnetd service which is responsible for handling remote terminal connections, making it a prime target for exploitation in environments where telnet services are actively running.
The technical flaw manifests through improper handling of environmental variables that control telnetd's operational behavior. When telnetd initializes and processes incoming connections, it fails to properly sanitize or validate environmental variables that are passed to the service. Local users can manipulate these variables to influence how telnetd operates, potentially leading to arbitrary code execution or privilege escalation. This vulnerability falls under the category of environment variable manipulation attacks, which are classified as CWE-15 - External Control of Critical State Variable within the Common Weakness Enumeration framework. The flaw essentially allows attackers to inject malicious values into critical system parameters that should remain under system control.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it provides attackers with complete system control through the telnet service. Since telnetd typically runs with elevated privileges to handle user connections and system access, the ability to manipulate its environmental variables creates a direct path to root access. This presents significant risk in multi-user environments where telnet services are enabled, as any local user could potentially exploit this flaw to gain unauthorized administrative access. The vulnerability is particularly concerning because it requires minimal privileges to exploit, as the attacker only needs local access to the system, making it a low-barrier privilege escalation vector that could be leveraged in various attack scenarios.
Mitigation strategies for CVE-2001-0093 should focus on immediate system hardening and service management. The most effective immediate solution involves disabling or removing the telnet service from systems where it is not absolutely required, as telnet inherently presents numerous security risks beyond this specific vulnerability. System administrators should implement proper environmental variable sanitization and validation within the telnetd service configuration, ensuring that critical variables cannot be manipulated by local users. Additionally, implementing the principle of least privilege by running telnetd with minimal required permissions and employing proper access controls can significantly reduce the attack surface. From an operational security perspective, this vulnerability aligns with tactics described in the MITRE ATT&CK framework under privilege escalation techniques, specifically focusing on environment variable manipulation and service configuration attacks. Regular security audits and system monitoring should be implemented to detect unauthorized modifications to critical system services and environmental configurations. The vulnerability also highlights the importance of proper input validation and secure coding practices, as recommended by industry standards including the OWASP Top Ten and NIST cybersecurity guidelines, which emphasize the need for robust sanitization of all system inputs and environment variables to prevent such exploitation vectors.