CVE-2010-2192 in pmount
Summary
by MITRE
The make_lockdir_name function in policy.c in pmount 0.9.18 allow local users to overwrite arbitrary files via a symlink attack on a file in /var/lock/.
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Analysis
by VulDB Data Team • 09/18/2021
The vulnerability identified as CVE-2010-2192 resides within the pmount utility version 0.9.18, specifically in the make_lockdir_name function located in policy.c. This flaw represents a classic symlink attack scenario that exploits insecure temporary file handling practices. The vulnerability occurs when pmount creates lock directory names in the /var/lock/ directory, where local users can manipulate symbolic links to redirect file operations to arbitrary locations on the filesystem. This type of vulnerability falls under the category of insecure temporary file handling as classified by CWE-377, which specifically addresses the creation of temporary files with insecure permissions or predictable names that can be exploited by attackers.
The technical execution of this vulnerability involves a race condition where an attacker can create symbolic links in the /var/lock/ directory before pmount processes them, allowing the utility to write data to files that the attacker controls rather than the intended lock files. When pmount processes these lock directory names, it follows the symbolic links and writes to the target files specified by the attacker's symlinks, potentially overwriting critical system files or injecting malicious content. This attack vector is particularly dangerous because pmount typically runs with elevated privileges, making the potential impact of file overwrites significantly more severe than typical local privilege escalation attacks.
The operational impact of this vulnerability extends beyond simple file overwrites, as it can lead to privilege escalation and system compromise when combined with other attack vectors. An attacker who successfully exploits this vulnerability can manipulate the contents of files that pmount writes to, potentially including configuration files, log files, or even system binaries if the utility has sufficient privileges. This vulnerability aligns with ATT&CK technique T1068 which covers local privilege escalation through the exploitation of system vulnerabilities. The attack is particularly concerning because it requires minimal privileges to execute and can be leveraged by attackers to gain persistent access or cause denial of service conditions.
Mitigation strategies for CVE-2010-2192 should focus on implementing proper file access controls and eliminating race conditions in temporary file creation. System administrators should ensure that pmount is updated to versions that address this vulnerability, as the original 0.9.18 release contained the insecure implementation. Additional protective measures include implementing proper file permissions on the /var/lock/ directory, using atomic file operations, and employing proper file descriptor management to prevent symbolic link following during file operations. The vulnerability also highlights the importance of following secure coding practices such as those outlined in the CERT Secure Coding Standards, particularly those addressing file system security and race condition prevention. Organizations should also consider implementing monitoring for suspicious file creation patterns in critical directories and ensure that system utilities running with elevated privileges are regularly audited for similar insecure temporary file handling practices.