CVE-2005-2851 in smb4k
Summary
by MITRE
smb4k 0.4 and other versions before 0.6.3 allows local users to read sensitive files via a symlink attack on the (1) smb4k.tmp or (2) sudoers temporary files.
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Analysis
by VulDB Data Team • 06/11/2019
The vulnerability identified as CVE-2005-2851 affects smb4k version 0.4 and earlier versions prior to 0.6.3, presenting a significant security risk through improper handling of temporary files. This flaw enables local attackers to gain unauthorized access to sensitive system information by exploiting symbolic link attacks against specific temporary files used by the application. The vulnerability resides in the application's failure to properly validate or secure temporary file creation processes, creating a path for privilege escalation and information disclosure attacks.
The technical implementation of this vulnerability involves two primary attack vectors targeting specific temporary file locations. The first vector targets the smb4k.tmp file while the second targets sudoers temporary files, both of which are created with predictable names and insecure permissions. When smb4k creates these temporary files, it does not adequately verify the existence or ownership of these files before writing to them, allowing attackers to establish symbolic links with the same names in advance. This creates a race condition scenario where the attacker's symlink is followed instead of the legitimate temporary file, enabling unauthorized file access. The vulnerability is classified under CWE-377 as insecure temporary file creation and under CWE-59 as improper link resolution, both of which are well-documented weaknesses in software security design.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can potentially enable attackers to escalate privileges and access system resources that should remain restricted. Local users who can execute the smb4k application can leverage this weakness to read files that they would normally not have access to, potentially including system configuration files, authentication data, or other sensitive information. The attack requires local system access but does not need network connectivity or remote exploitation capabilities, making it particularly dangerous in multi-user environments where privilege separation is expected. This vulnerability aligns with ATT&CK technique T1059.001 for executing commands and T1078 for valid accounts, as it exploits legitimate application functionality to gain unauthorized access.
Mitigation strategies for this vulnerability primarily involve updating to smb4k version 0.6.3 or later, which contains fixes for the temporary file handling issues. System administrators should also implement proper file permissions and ensure that temporary file creation uses secure methods such as creating files with exclusive access modes and verifying file ownership before writing. Additional defensive measures include monitoring for suspicious temporary file creation patterns and implementing mandatory access controls through tools like SELinux or AppArmor. The fix typically involves implementing proper file descriptor management and ensuring that temporary files are created with appropriate permissions and atomic operations to prevent symlink attacks. Organizations should also consider implementing privilege separation techniques and regular security audits to identify similar weaknesses in other applications and system components.