CVE-1999-0618 in Host
Summary
by MITRE
The rexec service is running.
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Analysis
by VulDB Data Team • 06/12/2026
The rexec service represents a significant security vulnerability within network infrastructure, as it provides unauthenticated remote execution capabilities that can be exploited by malicious actors to gain unauthorized access to systems. This service operates on port 512 and utilizes the remote execution protocol that was historically designed for legitimate administrative purposes but has become a prime target for exploitation due to its inherent security flaws. The service allows remote users to execute commands on the target system without proper authentication, creating an immediate and severe risk to system integrity and confidentiality. According to the CWE database, this vulnerability maps directly to CWE-250 which describes "Execute Code or Commands with Improper Privilege Levels" and CWE-776 which addresses "Improper Restriction of XML External Entity Reference." The rexec service's design flaw stems from its lack of proper authentication mechanisms and its reliance on weak security protocols that were never intended to withstand modern cyber threats.
The technical implementation of rexec creates a dangerous attack surface that enables remote command execution without requiring valid credentials, making it particularly attractive to threat actors who seek to establish persistent access to target networks. The service operates by accepting connections on TCP port 512 and executing commands provided by remote users, often with elevated privileges depending on the system configuration. This vulnerability directly violates fundamental security principles outlined in the NIST Cybersecurity Framework and aligns with ATT&CK technique T1059.001 which covers "Command and Scripting Interpreter: PowerShell" and T1068 which addresses "Exploitation for Privilege Escalation." The service's operation can be exploited through various attack vectors including network scanning to identify active instances, followed by exploitation of the service to execute malicious payloads. The lack of encryption in the rexec protocol means that credentials and commands are transmitted in plaintext, making them susceptible to interception and manipulation by network-based attackers.
The operational impact of an active rexec service extends far beyond simple unauthorized access, as it provides attackers with a persistent backdoor that can be used to establish long-term presence within target networks. This service can serve as an initial access point for more sophisticated attacks, enabling threat actors to deploy additional malware, conduct reconnaissance, or establish command and control channels. The vulnerability creates immediate risks for data integrity, confidentiality, and availability, as attackers can execute arbitrary code, modify system files, and potentially escalate privileges to gain administrative access. Organizations may experience significant operational disruption when rexec services are exploited, as attackers can use the service to move laterally within networks, access sensitive data, and maintain persistent access for extended periods. The vulnerability also creates compliance issues for organizations that must adhere to regulatory requirements such as the Payment Card Industry Data Security Standard (PCI DSS) and the Health Insurance Portability and Accountability Act (HIPAA) which mandate secure network services and access controls.
Mitigation strategies for rexec service vulnerabilities must include immediate service removal or disabling, as the service represents an inherently insecure protocol that cannot be adequately secured through configuration changes alone. Organizations should implement network segmentation to isolate systems that may be running rexec services and deploy firewalls to block traffic on port 512. The implementation of proper access controls and authentication mechanisms should replace the rexec service functionality with secure alternatives such as SSH or other encrypted remote execution protocols. Security monitoring should include detection of rexec service usage through network traffic analysis and endpoint monitoring to identify potential exploitation attempts. According to the MITRE ATT&CK framework, organizations should implement defensive techniques such as network traffic filtering and application whitelisting to prevent unauthorized execution of rexec commands. The remediation process should involve comprehensive system scanning to identify all instances of rexec service deployment, followed by complete removal of the service and replacement with secure alternatives that provide proper authentication and encryption mechanisms. Regular vulnerability assessments and penetration testing should be conducted to ensure that no instances of rexec service remain operational within the network infrastructure.