CVE-2002-0557 in OpenBSD
Summary
by MITRE
Vulnerability in OpenBSD 3.0, when using YP with netgroups in the password database, causes (1) rexec or (2) rsh to run another user s shell, or (3) atrun to change to a different user s directory, possibly due to memory allocation failures or an incorrect call to auth_approval().
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Analysis
by VulDB Data Team • 07/11/2014
This vulnerability exists in OpenBSD version 3.0 within the Yellow Pages (YP) subsystem when processing netgroups in the password database. The flaw manifests through three distinct attack vectors that leverage memory allocation failures or improper authentication approval mechanisms. The vulnerability stems from inadequate handling of user authentication contexts when YP services interact with the password database, creating opportunities for privilege escalation and unauthorized access to system resources. The root cause lies in the improper validation of user credentials and directory contexts during remote execution operations, particularly affecting services that rely on YP for user authentication and authorization.
The technical implementation of this vulnerability involves memory allocation failures that occur when YP processes netgroup information for password database entries. When rexec, rsh, or atrun services are invoked, the system fails to properly validate user contexts, allowing malicious actors to potentially execute commands under different user privileges or access alternative user directories. This occurs due to an incorrect call to auth_approval() function which should validate authentication credentials but instead permits unauthorized access through flawed memory handling. The vulnerability specifically impacts the authentication flow where YP services attempt to resolve user information and establish proper execution contexts. The flaw represents a classic case of improper access control where authentication mechanisms fail to properly isolate user sessions, allowing cross-user privilege escalation.
The operational impact of CVE-2002-0557 extends beyond simple privilege escalation to encompass potential data exposure and system compromise. Attackers can leverage this vulnerability to execute arbitrary commands with elevated privileges, access sensitive user directories, or gain unauthorized access to system resources that should be restricted to specific user groups. The vulnerability affects critical system services including remote execution capabilities and scheduled task execution, making it particularly dangerous in multi-user environments where system integrity is paramount. This weakness creates persistent security gaps that could allow attackers to maintain long-term access to compromised systems while potentially remaining undetected through normal monitoring procedures.
Mitigation strategies for this vulnerability require immediate system updates to patched versions of OpenBSD that address the YP authentication handling flaws. System administrators should implement strict access controls for YP services and ensure proper network segmentation to limit exposure to trusted networks only. The recommended approach includes disabling unnecessary YP services, implementing robust authentication auditing, and monitoring for unauthorized access attempts to system resources. Additionally, organizations should consider implementing alternative authentication mechanisms that do not rely on potentially vulnerable YP implementations. This vulnerability aligns with CWE-284 access control weaknesses and maps to ATT&CK techniques involving privilege escalation and credential access, emphasizing the need for comprehensive security hardening measures. Regular security assessments should verify that YP configurations properly enforce user isolation and authentication boundaries to prevent exploitation of similar memory allocation and authentication approval flaws.