CVE-2011-1834 in ecryptfs-utils
Summary
by MITRE
utils/mount.ecryptfs_private.c in ecryptfs-utils before 90 does not properly maintain the mtab file during error conditions, which allows local users to cause a denial of service (table corruption) or bypass intended unmounting restrictions via a umount system call.
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Analysis
by VulDB Data Team • 02/01/2022
The vulnerability identified as CVE-2011-1834 resides within the ecryptfs-utils package version 90 and earlier, specifically in the utils/mount.ecryptfs_private.c component. This flaw represents a significant security issue affecting encrypted filesystem operations on Linux systems. The ecryptfs implementation provides transparent encryption for filesystems, allowing users to encrypt their data at rest while maintaining normal file access patterns. The mtab file serves as a critical system resource that maintains a list of currently mounted filesystems, making its integrity essential for proper system operation and security controls.
The technical flaw manifests when the mount.ecryptfs_private.c utility fails to properly maintain the mtab file during error conditions that occur during the mounting process. When a mounting operation encounters an error, the utility should ensure that the mtab file remains consistent and properly updated to reflect the actual state of mounted filesystems. However, in vulnerable versions, this consistency is not maintained, leading to potential corruption of the mtab table. This corruption occurs because the utility does not properly handle cleanup operations when errors arise, leaving the mtab file in an inconsistent state that can be exploited by local attackers.
The operational impact of this vulnerability extends beyond simple denial of service conditions to include potential bypass of intended security restrictions. Local attackers can exploit this flaw by executing umount system calls that manipulate the corrupted mtab file, potentially allowing them to bypass the normal unmounting restrictions that ecryptfs implements. This creates a scenario where unauthorized users could gain access to encrypted data or disrupt normal system operations. The vulnerability is particularly concerning because it operates at the filesystem level and can be exploited by users with minimal privileges, making it a significant concern for system administrators managing encrypted environments.
This vulnerability aligns with CWE-119, which describes improper restriction of operations within a memory buffer, and represents a specific instance of inadequate error handling in system utilities. The flaw also relates to ATT&CK technique T1490, which involves data destruction and denial of service through manipulation of system resources. The mtab file corruption creates a condition where system integrity is compromised, potentially allowing attackers to manipulate the filesystem state to their advantage. The security implications extend to privilege escalation scenarios where local users might exploit this flaw to gain unauthorized access to encrypted data or disrupt system services that depend on proper filesystem state management.
Mitigation strategies for CVE-2011-1834 require immediate patching of the ecryptfs-utils package to version 90 or later, where the mtab file handling has been corrected. System administrators should also implement monitoring of mtab file integrity and establish regular verification procedures to detect corruption. Additional defensive measures include restricting access to mount and umount system calls, implementing proper file permissions for the mtab file, and maintaining regular system audits to identify any potential exploitation attempts. Organizations should also consider implementing automated patch management systems to ensure timely deployment of security updates across all affected systems.