CVE-2009-0872 in OpenSolaris
Summary
by MITRE
The NFS server in Sun Solaris 10, and OpenSolaris before snv_111, does not properly implement the AUTH_NONE (aka sec=none) security mode in combination with other security modes, which allows remote attackers to bypass intended access restrictions and read or modify files, as demonstrated by a combination of the AUTH_NONE and AUTH_SYS security modes.
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Analysis
by VulDB Data Team • 08/31/2019
The vulnerability described in CVE-2009-0872 represents a critical security flaw in the Network File System implementation within Sun Solaris 10 and OpenSolaris versions prior to snv_111. This issue specifically targets the authentication mechanisms that govern how NFS servers handle different security modes, creating a dangerous misconfiguration that undermines the intended access controls. The flaw manifests when the server fails to properly enforce security boundaries between different authentication methods, allowing malicious actors to exploit the system's permissive handling of AUTH_NONE (sec=none) mode in conjunction with more restrictive security modes.
The technical implementation of this vulnerability stems from improper validation of authentication contexts within the NFS server daemon. When a client connects using AUTH_NONE, the system should enforce strict access controls that prevent unauthorized data access. However, the flaw allows the system to accept connections that appear to use one security mode while actually operating under a more permissive context. This creates a scenario where a remote attacker can manipulate the authentication sequence to gain access to resources that should be restricted to authenticated users only. The vulnerability specifically impacts the interaction between AUTH_NONE and AUTH_SYS modes, where the server's security enforcement logic fails to properly distinguish between different authentication contexts.
The operational impact of this vulnerability is severe and far-reaching, as it allows remote attackers to bypass intended access restrictions and perform unauthorized operations on the affected system. An attacker could potentially read sensitive files, modify critical data, or even execute arbitrary code depending on the permissions granted to the NFS shares. This represents a direct violation of the principle of least privilege and can lead to complete system compromise if the NFS shares contain sensitive system files or user data. The vulnerability is particularly dangerous because it can be exploited remotely without requiring any prior authentication credentials, making it a high-value target for attackers seeking to gain unauthorized access to enterprise networks.
Mitigation strategies for this vulnerability should focus on immediate system updates and configuration changes. Organizations must upgrade to patched versions of Solaris 10 and OpenSolaris that address this specific authentication flaw. In the interim, administrators should disable the AUTH_NONE security mode on NFS exports and enforce strict authentication requirements for all NFS services. The use of network segmentation and firewall rules to restrict NFS traffic to trusted networks can provide additional defense-in-depth. This vulnerability aligns with CWE-284, which addresses improper access control in software systems, and maps to ATT&CK technique T1077 for the use of remote services and T1046 for network service scanning. Organizations should also implement monitoring for unusual NFS access patterns and ensure that all NFS services are properly audited for authentication enforcement. The vulnerability demonstrates the importance of proper security context management and the critical need for thorough testing of authentication mechanisms in network services.