CVE-1999-1059 in TCP
Summary
by MITRE
vulnerability in rexec daemon (rexecd) in at&t tcp/ip 4.0 for various svr4 systems allows remote attackers to execute arbitrary commands.
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Analysis
by VulDB Data Team • 06/07/2024
The CVE-1999-1059 vulnerability represents a critical security flaw in the rexec daemon implementation within AT&T TCP/IP 4.0 for various SVR4 systems. This vulnerability stems from the insecure design of the rexec protocol which was intended to provide remote command execution capabilities but failed to implement proper authentication mechanisms. The rexec daemon operates on TCP port 512 and allows users to execute commands on remote systems without adequate verification of credentials, creating a fundamental security weakness that has persisted across multiple Unix-based systems.
The technical flaw in this vulnerability resides in the daemon's failure to properly authenticate remote connections before executing commands. When a client connects to the rexec daemon, the service accepts commands based solely on the client's ability to establish a network connection without requiring proper user authentication or authorization checks. This design flaw allows malicious actors to exploit the service by simply connecting to the daemon and issuing commands that are executed with the privileges of the rexec daemon process, which typically runs with elevated system privileges. The vulnerability is classified under CWE-284, which addresses improper access control issues in software implementations, and aligns with ATT&CK technique T1059.001 for command and script injection attacks.
The operational impact of CVE-1999-1059 is severe and far-reaching, as it enables remote code execution without requiring any valid user credentials or authentication. Attackers can exploit this vulnerability to gain unauthorized access to systems, execute arbitrary commands, and potentially escalate privileges to root level access. The vulnerability affects a wide range of SVR4-based systems including various Unix implementations that shipped with AT&T TCP/IP 4.0, making it particularly dangerous given the prevalence of these systems in enterprise environments during the late 1990s. This weakness can be exploited for reconnaissance, data exfiltration, system compromise, and lateral movement within network environments, as it provides an unauthenticated path for attackers to execute malicious commands on target systems.
Mitigation strategies for CVE-1999-1059 involve multiple layers of security controls to address the fundamental flaw in the rexec protocol implementation. The primary recommendation is to disable or remove the rexec daemon from systems where it is not absolutely required, as the protocol itself is inherently insecure and has been deprecated in favor of more secure alternatives. Organizations should implement network segmentation to prevent unauthorized access to systems running rexec services and ensure that TCP port 512 is not accessible from untrusted networks. Additionally, system administrators should consider implementing firewall rules to block incoming connections on port 512 and replace rexec with secure alternatives such as SSH (Secure Shell) which provides proper authentication and encryption mechanisms. The vulnerability demonstrates the importance of following security best practices outlined in NIST guidelines for secure system configuration and the principle of least privilege in system design.