CVE-2015-3400 in sharenfs
Summary
by MITRE
sharenfs 0.6.4, when built with commits bcdd594 and 7d08880 from the zfs repository, provides world readable access to the shared zfs file system, which might allow remote authenticated users to obtain sensitive information by reading shared files.
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Analysis
by VulDB Data Team • 01/03/2023
The vulnerability identified as CVE-2015-3400 affects the sharenfs utility version 0.6.4 when compiled with specific commits from the zfs repository. This flaw represents a significant security weakness in network file system sharing configurations where proper access controls fail to prevent unauthorized data exposure. The vulnerability stems from improper permission handling within the nfs sharing implementation that allows any authenticated remote user to access files that should remain restricted, creating a scenario where sensitive information can be read by individuals who should not have such privileges.
The technical root cause of this vulnerability lies in the flawed implementation of file system permissions within the sharenfs utility. When the utility is built with the specified zfs repository commits, it fails to properly enforce access controls that would normally restrict file access to authorized users only. This creates a world-readable condition where files within the shared zfs filesystem become accessible to any authenticated user who can establish an nfs connection to the system. The vulnerability specifically affects the permission model implementation and represents a failure in proper access control enforcement that aligns with common weakness patterns described in CWE-284, which addresses improper access control issues.
From an operational perspective, this vulnerability poses a substantial risk to organizations relying on zfs-based nfs sharing services. Remote authenticated users can exploit this flaw to read sensitive files that should remain protected within the shared filesystem, potentially exposing confidential data, system configurations, or user information. The impact extends beyond simple information disclosure as it undermines the fundamental security model of the file sharing system, allowing unauthorized data access that could lead to further exploitation or compromise of other system components. This vulnerability affects systems where zfs filesystems are shared via nfs and where proper access control mechanisms have been bypassed due to the flawed implementation.
Security mitigations for this vulnerability should focus on immediate remediation through updated software versions that address the permission handling flaws in the sharenfs utility. Organizations should ensure they are running patched versions of the zfs utilities and avoid building the sharenfs component with the problematic commits mentioned in the vulnerability description. Network segmentation and firewall rules can provide temporary protection by limiting access to nfs services, though this does not address the core permission issue. The vulnerability demonstrates the importance of proper access control implementation in distributed file systems and highlights the need for regular security auditing of system components that handle file sharing operations. This issue also aligns with ATT&CK technique T1005, which involves data from local system, as unauthorized access to shared files represents a method of information gathering that could be leveraged for further attacks. System administrators should conduct thorough audits of their nfs sharing configurations and ensure that proper access controls are enforced to prevent unauthorized file access.