CVE-2017-14387 in Isilon OneFS
Summary
by MITRE
The NFS service in EMC Isilon OneFS 8.1.0.0, 8.0.1.0 - 8.0.1.1, and 8.0.0.0 - 8.0.0.4 maintains default NFS export settings (including the NFS export security flavor for authentication) that can be leveraged by current and future NFS exports. This NFS service contained a flaw that did not properly propagate changes made to the default security flavor to all new and existing NFS exports that are configured to use default NFS export settings and that are mounted after those changes are made. This flaw may potentially allow NFS clients to access affected NFS exports using the default and potentially weaker security flavor even if a more secure one was selected to be used by the OneFS administrator, aka an "NFS Export Security Setting Fallback Vulnerability."
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Analysis
by VulDB Data Team • 12/28/2019
The CVE-2017-14387 vulnerability represents a critical security flaw in EMC Isilon OneFS NFS services affecting versions 8.1.0.0 through 8.0.0.4. This issue manifests as a configuration propagation failure where the system fails to properly apply security settings changes to existing and newly created NFS exports that utilize default export settings. The vulnerability operates at the intersection of network file system security and configuration management, creating a persistent backdoor that undermines administrative security decisions. The flaw specifically targets the NFS export security flavor authentication mechanism, which is fundamental to protecting network file system access controls. According to CWE-284, this represents an improper access control vulnerability where the system fails to properly enforce security settings that should be consistently applied across all export points. The vulnerability's impact extends beyond immediate access control to encompass long-term security posture degradation, as the default security settings remain active even after administrators have explicitly configured stronger authentication mechanisms.
The technical implementation of this vulnerability stems from a failure in the NFS service's configuration management system where security flavor changes are not properly propagated to all NFS export instances. When administrators modify the default NFS export security settings, the system fails to update existing exports that were configured to use default parameters, while also failing to apply these changes to new exports created after the modification. This creates a scenario where the system maintains multiple security contexts simultaneously, with default settings taking precedence over explicitly configured secure settings. The flaw essentially creates a fallback mechanism that automatically reverts to weaker security configurations when the system cannot properly maintain the intended security posture. This behavior aligns with ATT&CK technique T1078.004, which describes valid accounts being used to gain access to systems, as the vulnerability allows unauthorized access through default security settings that should have been overridden. The vulnerability's persistence across system restarts and configuration changes makes it particularly dangerous as it can remain active even after administrators believe they have corrected the security configuration.
The operational impact of CVE-2017-14387 is significant for organizations relying on EMC Isilon storage systems, as it creates potential unauthorized access to sensitive data through NFS mounts. Attackers can exploit this vulnerability by mounting NFS exports that were configured to use default security settings, thereby bypassing the more secure authentication mechanisms that administrators intended to enforce. This vulnerability particularly affects environments where multiple security levels are configured and where administrative changes are expected to be immediately effective. The flaw undermines trust in the system's security controls and creates a persistent risk that can be exploited by both internal and external threat actors. Organizations using the affected versions of OneFS may experience unauthorized data access, potential data exfiltration, and violation of compliance requirements that mandate specific security controls for network file system access. The vulnerability's impact is amplified in environments where NFS is used for critical data access and where administrative access to storage systems is limited to authorized personnel only.
Mitigation strategies for CVE-2017-14387 require immediate attention through system updates and configuration hardening measures. Organizations should apply the latest security patches provided by EMC to address the underlying configuration propagation issue in the OneFS NFS service. Until patches are applied, administrators should manually verify and enforce consistent security settings across all NFS exports, ensuring that default settings are explicitly configured to match the intended security posture. The vulnerability highlights the importance of implementing configuration management practices that can detect and correct such propagation failures, including regular audits of NFS export settings and monitoring for unauthorized access attempts. Security teams should implement network segmentation to limit NFS access to authorized systems and establish monitoring procedures that can detect when default security settings are being used instead of configured secure settings. Additionally, organizations should consider implementing automated configuration management tools that can enforce security policies consistently across all export points, preventing the manual configuration errors that contribute to this vulnerability. The remediation process should include thorough testing of NFS export configurations to ensure that security settings are properly propagated and that no exports remain vulnerable to the fallback mechanism.