CVE-2011-1585 in Linux
Summary
by MITRE
The cifs_find_smb_ses function in fs/cifs/connect.c in the Linux kernel before 2.6.36 does not properly determine the associations between users and sessions, which allows local users to bypass CIFS share authentication by leveraging a mount of a share by a different user.
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Analysis
by VulDB Data Team • 01/03/2022
The vulnerability identified as CVE-2011-1585 resides within the Linux kernel's CIFS (Common Internet File System) implementation, specifically in the cifs_find_smb_ses function located in fs/cifs/connect.c. This flaw represents a critical authentication bypass issue that fundamentally undermines the security model of CIFS share access. The vulnerability affects Linux kernel versions prior to 2.6.36 and stems from improper handling of user-session associations within the CIFS subsystem. The technical root cause lies in the kernel's failure to properly validate and maintain the relationship between user credentials and established SMB sessions, creating a scenario where authentication contexts can be incorrectly shared or misinterpreted.
The operational impact of this vulnerability is significant for systems utilizing CIFS shares, as it allows local users to exploit a fundamental security gap in the kernel's session management. When a user mounts a CIFS share, the kernel establishes a session that should be uniquely tied to that specific user's credentials. However, due to the flawed implementation, a malicious local user can leverage an existing mount operation performed by a different user to gain unauthorized access to resources that should be restricted. This creates a scenario where the authentication mechanism can be bypassed through session reuse or improper session association, effectively allowing privilege escalation and unauthorized data access.
This vulnerability maps directly to CWE-284, which describes improper access control in software systems, and aligns with ATT&CK technique T1068, which covers 'Exploitation for Privilege Escalation' through local system exploitation. The flaw essentially creates a path for local privilege escalation by allowing users to manipulate session associations and gain access to resources that should be protected by proper authentication boundaries. The vulnerability is particularly dangerous because it operates at the kernel level, meaning that exploitation does not require network access or external attack vectors, making it a purely local privilege escalation issue.
The mitigation strategy for CVE-2011-1585 involves upgrading to Linux kernel version 2.6.36 or later, where the session management logic has been corrected to properly associate users with their respective sessions. System administrators should also implement proper monitoring of CIFS mount operations and user session tracking to detect anomalous behavior. Additional protective measures include restricting local user access to CIFS mount points, implementing proper user isolation, and regularly auditing authentication logs for unauthorized session usage patterns. The vulnerability demonstrates the critical importance of proper session management in network authentication systems and highlights the potential for kernel-level flaws to create widespread security implications across all systems utilizing the affected functionality.