CVE-2005-3623 in Linux
Summary
by MITRE
nfs2acl.c in the Linux kernel 2.6.14.4 does not check for MAY_SATTR privilege before setting access controls (ACL) on files on exported NFS filesystems, which allows remote attackers to bypass ACLs for readonly mounted NFS filesystems.
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Analysis
by VulDB Data Team • 06/21/2025
The vulnerability described in CVE-2005-3623 represents a critical access control flaw in the Linux kernel's NFS implementation that undermines the security of network file systems. This issue exists within the nfs2acl.c file of kernel version 2.6.14.4 and affects how access controls are managed on NFS exported filesystems. The flaw specifically targets the privilege checking mechanism that should enforce proper access permissions when setting file attributes and access controls. When a client mounts an NFS filesystem in read-only mode, the system should prevent any modifications to file permissions or access control lists. However, this vulnerability allows remote attackers to circumvent these protective measures through improper privilege validation during the attribute setting process.
The technical implementation of this vulnerability stems from the absence of proper privilege validation in the nfs2acl.c component, which handles the translation between NFS access control lists and the Linux kernel's native access control mechanisms. The kernel fails to verify whether the calling process possesses the necessary MAY_SATTR privilege before allowing access control modifications on files within exported NFS filesystems. This missing validation occurs regardless of the mount options specified by the client, including read-only mounts that should prevent any attribute modifications. The flaw essentially creates a path where remote attackers can manipulate file permissions and access controls even when the filesystem is mounted with read-only restrictions, effectively bypassing the intended security boundaries.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it fundamentally compromises the integrity of network file system security models. Remote attackers can exploit this weakness to gain unauthorized access to files that should be protected by access controls, potentially leading to data exposure, modification, or complete compromise of the NFS export. The vulnerability is particularly dangerous because it operates at the kernel level, making it difficult to detect and remediate without proper system updates. Network-based attacks can leverage this flaw to modify file permissions, potentially elevating privileges or creating backdoors within the NFS environment. This weakness affects systems where NFS is used for shared file storage and can impact organizations relying on network file systems for data management and collaboration.
Mitigation strategies for CVE-2005-3623 require immediate kernel updates to address the privilege checking flaw in the NFS implementation. System administrators should apply the appropriate security patches released by kernel maintainers and ensure all NFS servers are updated to versions that properly validate MAY_SATTR privileges before allowing access control modifications. Organizations should also implement network segmentation and access controls to limit exposure to NFS services, particularly for read-only mounts where this vulnerability is most impactful. The vulnerability aligns with CWE-284 access control weaknesses and can be categorized under ATT&CK technique T1077 for path traversal and privilege escalation. Regular security audits of NFS configurations and monitoring for unauthorized access control modifications should be implemented as part of comprehensive security controls. Additionally, administrators should consider implementing network-level firewalls to restrict NFS traffic to trusted hosts and ensure that NFS exports are properly configured with appropriate security measures to prevent unauthorized access to file system resources.