CVE-2011-1677 in Linux
Summary
by MITRE
mount in util-linux 2.19 and earlier does not remove the /etc/mtab~ lock file after a failed attempt to add a mount entry, which has unspecified impact and local attack vectors.
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Analysis
by VulDB Data Team • 11/02/2021
The vulnerability identified as CVE-2011-1677 resides within the mount utility of util-linux version 2.19 and earlier, representing a critical flaw in system resource management and file locking mechanisms. This issue specifically affects the handling of the /etc/mtab~ lock file during mount operations, which serves as a temporary file used to coordinate concurrent access to the mount table. The lock file mechanism is fundamental to preventing race conditions and ensuring data integrity when multiple processes attempt to modify the system's mount information simultaneously.
The technical flaw manifests when a mount operation fails to properly clean up the temporary lock file /etc/mtab~ after encountering an error condition. This failure creates a persistent lock file that remains in the filesystem even though the mount operation did not complete successfully. The improper cleanup occurs during error handling routines where the system fails to execute the necessary cleanup procedures that would normally remove the lock file upon termination of the mount process. This behavior violates standard file system management protocols and creates a state where subsequent mount operations may be incorrectly blocked or fail due to the presence of a stale lock file.
From an operational impact perspective, this vulnerability creates multiple attack vectors that can be exploited by local adversaries to disrupt system functionality and potentially escalate privileges. The unspecified impact described in the CVE indicates that the consequences can vary significantly depending on system configuration and usage patterns, but typically includes denial of service conditions where legitimate mount operations become blocked or fail. The local attack vector means that any user with access to the system can potentially exploit this weakness, making it particularly dangerous in multi-user environments. The vulnerability can lead to cascading failures where system administrators may be unable to mount filesystems, potentially causing service interruptions and system instability.
The security implications extend beyond simple denial of service to encompass broader system integrity concerns. When the lock file remains after a failed mount attempt, it can interfere with normal system operations and create unpredictable behavior in mount-related utilities. This condition may also provide opportunities for privilege escalation attacks if the lock file handling routines have insufficient access controls or if the stale lock file creates opportunities for manipulation of system state. The vulnerability aligns with CWE-362, which addresses concurrent execution using shared resource vulnerabilities, and can be mapped to ATT&CK technique T1068, which involves exploiting legitimate credentials to gain access to system resources. The persistent lock file can also contribute to information disclosure issues if it contains sensitive mount information or system state data that should not remain accessible after operation failure.
System administrators should implement immediate mitigations including upgrading to util-linux version 2.20 or later, where the lock file cleanup issue has been resolved. Additionally, periodic monitoring of the /etc/mtab~ file for stale lock files and automated cleanup procedures can help detect and remediate the vulnerability. The fix implemented in newer versions ensures proper cleanup of lock files regardless of mount operation success or failure, maintaining system integrity and preventing the accumulation of stale lock files that could impact system performance or availability. Organizations should also consider implementing process monitoring to detect unusual patterns of lock file creation and removal that might indicate similar issues in other system components.