CVE-2001-0946 in Linux
Summary
by MITRE
apmscript in Apmd in Red Hat 7.2 "Enigma" allows local users to create or change the modification dates of arbitrary files via a symlink attack on the LOW_POWER temporary file, which could be used to cause a denial of service, e.g. by creating /etc/nologin and disabling logins.
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Analysis
by VulDB Data Team • 04/14/2019
The vulnerability identified as CVE-2001-0946 resides within the apmscript component of Apmd service in Red Hat Enterprise Linux 7.2 "Enigma" operating system. This flaw represents a classic symlink attack vector that exploits improper temporary file handling mechanisms within the application's file operations. The vulnerability specifically targets the LOW_POWER temporary file which serves as a critical system resource for power management operations. When local users manipulate the symbolic link structure pointing to this temporary file, they can effectively control the modification timestamps of arbitrary files within the system's filesystem hierarchy.
The technical implementation of this vulnerability stems from inadequate validation of temporary file creation processes within the apmscript utility. When the application processes power management operations, it creates temporary files without proper security checks to ensure that these files are not being manipulated through symbolic link attacks. This design flaw allows malicious local users to establish symbolic links that point to critical system files such as /etc/nologin, enabling them to modify the timestamps of these files without proper authorization. The vulnerability operates at the file system level and leverages the fundamental weakness in temporary file creation protocols that fail to account for potential symlink manipulation by unprivileged users.
The operational impact of this vulnerability extends beyond simple timestamp manipulation and can result in significant system disruption and denial of service conditions. By creating or modifying the modification dates of critical system files like /etc/nologin, attackers can effectively disable user logins and system access, thereby compromising system availability and user access. This attack vector can be particularly devastating in enterprise environments where system uptime and user access are critical for business operations. The vulnerability essentially allows a local user to escalate their privileges to the point where they can effectively lock out legitimate users and system administrators, creating a persistent denial of service condition that requires manual intervention to resolve.
Mitigation strategies for this vulnerability should focus on implementing proper temporary file creation mechanisms that prevent symbolic link attacks through the use of secure file creation patterns. The recommended approach involves utilizing system calls that guarantee atomic file creation and proper file descriptor management to ensure that temporary files are not susceptible to symlink manipulation. System administrators should also implement proper file system permissions and access controls to limit the ability of local users to create symbolic links that could target critical system files. This vulnerability aligns with CWE-377 which addresses insecure temporary file creation and CWE-378 which covers insecure temporary file creation with predictable names. From an attack framework perspective, this vulnerability maps to techniques described in the MITRE ATT&CK framework under the T1059 and T1499 tactics, representing command execution and denial of service capabilities respectively. The vulnerability demonstrates the critical importance of secure coding practices in system-level applications and highlights the need for comprehensive security testing of file operation handling mechanisms.