CVE-2006-2654 in FreeBSD
Summary
by MITRE
Directory traversal vulnerability in smbfs smbfs on FreeBSD 4.10 up to 6.1 allows local users to escape chroot restrictions for an SMB-mounted filesystem via "..\\" sequences. NOTE: this is similar to CVE-2006-1864, but this is a different implementation of smbfs, so it has a different CVE identifier.
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Analysis
by VulDB Data Team • 03/13/2021
The vulnerability described in CVE-2006-2654 represents a critical directory traversal flaw within the smbfs filesystem implementation on FreeBSD operating systems ranging from version 4.10 through 6.1. This security weakness specifically affects the SMB (Server Message Block) filesystem driver that enables FreeBSD systems to mount and access remote SMB shares. The issue arises from inadequate input validation and path resolution mechanisms within the smbfs component, creating a significant bypass opportunity for local attackers who possess access to the system.
The technical flaw manifests when users exploit "..\" sequences within SMB-mounted filesystems to escape the intended chroot restrictions that should contain filesystem access within designated boundaries. This directory traversal vulnerability allows malicious local users to navigate beyond the restricted filesystem mount points and potentially access unauthorized system resources, files, or directories that should remain protected. The vulnerability stems from improper handling of parent directory references in the filesystem path resolution logic, enabling attackers to manipulate path traversal sequences to gain elevated access privileges.
Operationally, this vulnerability poses a severe threat to system security as it allows local users to circumvent the intended security boundaries of SMB mounts. Attackers can leverage this flaw to access files and directories outside of the mounted SMB share, potentially leading to information disclosure, privilege escalation, or further exploitation of the compromised system. The impact extends beyond simple file access as it undermines the fundamental security model that chroot environments are designed to enforce, creating potential pathways for more sophisticated attacks. This vulnerability directly violates security principles established in the Common Weakness Enumeration framework under CWE-22, which catalogs improper limitation of a pathname to a restricted directory.
The exploitation of this vulnerability demonstrates a clear attack pattern that aligns with techniques documented in the MITRE ATT&CK framework under the privilege escalation and defense evasion domains. Attackers can use this weakness to bypass security controls and access sensitive system information, making it particularly dangerous in multi-user environments where different users may have varying levels of access rights. The vulnerability's persistence across multiple FreeBSD versions from 4.10 to 6.1 indicates a fundamental flaw in the smbfs implementation that required systematic patching across the affected platform versions.
Mitigation strategies for CVE-2006-2654 primarily involve applying the appropriate security patches released by FreeBSD for the affected versions, which typically address the path traversal logic in the smbfs component. System administrators should ensure that all FreeBSD systems are updated to versions that contain the necessary fixes, as the vulnerability remains exploitable in unpatched systems. Additionally, implementing restrictive filesystem mount options and limiting local user access to SMB mounts can reduce the attack surface. Network administrators should also consider monitoring for unusual filesystem access patterns that might indicate exploitation attempts. The vulnerability highlights the importance of proper input validation and path resolution in filesystem implementations, emphasizing the need for robust security testing and code review processes to prevent similar issues in other filesystem drivers and security-critical system components.