CVE-2000-0532 in FreeBSD
Summary
by MITRE
A FreeBSD patch for SSH on 2000-01-14 configures ssh to listen on port 722 as well as port 22, which might allow remote attackers to access SSH through port 722 even if port 22 is otherwise filtered.
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Analysis
by VulDB Data Team • 03/24/2017
This vulnerability originates from a FreeBSD security patch released on January 14 2000 that inadvertently configured the Secure Shell daemon to listen on both the standard SSH port 22 and an additional non-standard port 722. The flaw represents a misconfiguration issue that fundamentally alters the network accessibility of the SSH service by creating an unexpected attack surface. The vulnerability stems from the patch's implementation where administrators who applied the update found their systems listening on two ports instead of the single standard port, creating a potential security risk when the primary port 22 is filtered by firewalls or network access controls. This configuration change violates the principle of least privilege and creates an unintended network exposure that adversaries could exploit to bypass traditional network filtering mechanisms. The technical flaw falls under the category of improper system configuration and can be mapped to CWE-255 Improper Credential Handling, as it creates a situation where authentication mechanisms may be accessible through unexpected network paths.
The operational impact of this vulnerability extends beyond simple network accessibility issues as it creates confusion in security monitoring and incident response procedures. When network security policies are designed to restrict access to port 22, the presence of port 722 creates a potential backdoor that security teams might not be aware of, leading to gaps in network defense. This vulnerability specifically aligns with ATT&CK technique T1068 Exploitation for Privilege Escalation as it provides an alternative path for attackers to establish connections to SSH services. The presence of multiple listening ports also complicates network segmentation efforts and can cause issues with network intrusion detection systems that may not be configured to monitor non-standard ports for SSH traffic. Additionally, this misconfiguration can lead to confusion during security audits and compliance assessments where network port scanning might reveal unexpected open ports that could trigger false positives or indicate potential security gaps.
The mitigation strategy for this vulnerability requires immediate administrative action to review and correct the SSH service configuration. System administrators must verify that the ssh daemon is configured to listen only on the intended port and remove any unintended listening ports from the configuration files. The fix involves editing the sshd_config file to ensure that only port 22 is specified in the Port directive, and any references to port 722 must be removed or commented out. Organizations should implement comprehensive network scanning procedures to identify any systems that may have been affected by this patch and ensure that all SSH services are properly configured according to security best practices. Regular security audits should include verification of service configurations to prevent similar misconfigurations from occurring in the future. The vulnerability also highlights the importance of maintaining detailed change management procedures for security patches and the necessity of testing updates in controlled environments before deployment to production systems. This incident demonstrates how seemingly minor configuration changes in security patches can create significant operational security risks and emphasizes the need for thorough testing and validation of all system modifications.