CVE-2009-0873 in OpenSolaris
Summary
by MITRE
The NFS daemon (aka nfsd) in Sun Solaris 10 and OpenSolaris before snv_106, when NFSv3 is used, does not properly implement combinations of security modes, which allows remote attackers to bypass intended access restrictions and read or modify files, as demonstrated by a combination of the sec=sys and sec=krb5 security modes, related to modes that "override each other."
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Analysis
by VulDB Data Team • 08/31/2019
The vulnerability identified as CVE-2009-0873 represents a critical flaw in the Network File System daemon implementation within Sun Solaris 10 and OpenSolaris systems prior to snv_106. This issue specifically affects NFSv3 protocol implementations where the daemon fails to properly handle the interaction between different security modes, creating a scenario where access controls can be circumvented through deliberate configuration combinations. The vulnerability stems from the improper handling of security mode overrides, which allows unauthorized access to file systems through crafted NFS requests that exploit the inconsistent behavior between different security mechanisms.
The technical implementation flaw occurs when the NFS daemon processes requests that combine sec=sys and sec=krb5 security modes, where these modes should theoretically provide different levels of authentication and authorization controls. However, due to inadequate mode handling logic, the security mechanisms interfere with each other in a way that allows attackers to bypass intended access restrictions. This creates a situation where the system's security posture is weakened rather than strengthened when multiple security modes are configured simultaneously, as the override behavior causes the more restrictive security mode to be effectively ignored or superseded by another mode in the combination.
The operational impact of this vulnerability is significant for systems running affected versions of Solaris, as it enables remote attackers to gain unauthorized access to file systems that should be protected by the configured security modes. Attackers can potentially read sensitive data or modify files that should be restricted to authorized users only, depending on the specific combination of security modes that can be exploited. This vulnerability particularly affects enterprise environments where Solaris systems are commonly used for file sharing and network storage services, potentially leading to data breaches, unauthorized modifications, and compromise of system integrity. The remote nature of the attack means that exploitation does not require physical access to the system, making it a particularly dangerous vulnerability in networked environments.
The vulnerability aligns with CWE-284 Access Control Issues, specifically addressing improper access control mechanisms in security implementation, and relates to ATT&CK technique T1078 Valid Accounts for maintaining persistent access through legitimate credentials. Organizations should implement immediate mitigations including updating to patched versions of Solaris, disabling unnecessary security modes, and implementing network segmentation to limit exposure. System administrators should also monitor for suspicious NFS activity and review security mode configurations to ensure that conflicting security settings are not enabled simultaneously. The vulnerability demonstrates the importance of thorough testing of security mode interactions in network services and highlights the risks associated with complex security configurations that may create unexpected behavior patterns in access control implementations.