CVE-2002-0765 in OpenSSH
Summary
by MITRE
sshd in OpenSSH 3.2.2, when using YP with netgroups and under certain conditions, may allow users to successfully authenticate and log in with another user s password.
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Analysis
by VulDB Data Team • 05/16/2019
The vulnerability identified as CVE-2002-0765 represents a critical authentication flaw in the OpenSSH implementation that affects versions 3.2.2 and earlier. This issue specifically manifests within the sshd daemon when utilizing Yellow Pages (YP) directory services combined with netgroups for user authentication. The flaw stems from improper handling of authentication requests that should have been rejected based on the YP netgroup membership validation process. When users attempt to authenticate through sshd using YP netgroup functionality, the system fails to properly validate whether the requesting user belongs to the appropriate netgroup, potentially allowing unauthorized access through credential substitution attacks.
The technical root cause of this vulnerability lies in the insufficient validation of netgroup membership during the authentication process. In YP environments, netgroups serve as logical collections of users and hosts that define access permissions and authentication boundaries. When OpenSSH 3.2.2 processes authentication requests, it incorrectly processes the netgroup membership checks, particularly when dealing with user credentials that may have been manipulated or substituted. This flaw creates a path where an attacker could potentially authenticate using another user's password if the system fails to properly enforce netgroup membership restrictions. The vulnerability specifically occurs under certain conditions that involve the interaction between the sshd daemon's authentication routines and the YP netgroup resolution mechanisms, making it particularly challenging to detect and prevent through standard security measures.
The operational impact of CVE-2002-0765 extends beyond simple unauthorized access, as it fundamentally undermines the authentication integrity of systems relying on YP netgroup services. Organizations utilizing OpenSSH 3.2.2 with YP integration face potential security breaches where attackers could gain access to sensitive systems using legitimate user credentials from other accounts. This vulnerability aligns with CWE-287, which addresses improper authentication issues in authentication systems, and represents a significant weakness in the authentication framework that could enable privilege escalation attacks. The flaw particularly affects environments where YP netgroups are used for access control, creating opportunities for attackers to exploit the system's trust relationships and potentially gain unauthorized access to resources that should be restricted to specific user groups.
Systems most vulnerable to this flaw include enterprise environments that depend on YP directory services for user management and authentication, particularly those running OpenSSH 3.2.2 or earlier versions. The attack vector requires knowledge of existing user accounts within the YP directory and specific conditions related to netgroup membership, making it more targeted than broad authentication bypass vulnerabilities. Organizations should consider implementing immediate mitigation strategies including upgrading to patched versions of OpenSSH, disabling YP netgroup functionality where possible, and implementing additional authentication layers such as two-factor authentication or certificate-based authentication. The vulnerability demonstrates the importance of proper access control validation and highlights the risks associated with legacy authentication mechanisms that may not adequately address modern security requirements. This flaw serves as a reminder of the critical importance of maintaining up-to-date security software and implementing comprehensive authentication policies that account for potential weaknesses in directory service integrations.
The vulnerability also relates to ATT&CK technique T1078 which covers valid accounts and privilege escalation through legitimate authentication methods. Organizations should review their authentication configurations and implement monitoring for unusual authentication patterns that might indicate exploitation attempts. Security teams should also consider the broader implications of YP-based authentication systems and evaluate whether alternative authentication mechanisms provide better security guarantees. The incident underscores the necessity of thorough security testing for authentication components and the importance of validating access control mechanisms in complex directory service environments where multiple authentication layers interact.