CVE-2014-3519 in Linux
Summary
by MITRE
The open_by_handle_at function in vzkernel before 042stab090.5 in the OpenVZ modification for the Linux kernel 2.6.32, when using simfs, might allow local container users with CAP_DAC_READ_SEARCH capability to bypass an intended container protection mechanism and access arbitrary files on a filesystem via vectors related to use of the file_handle structure.
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Analysis
by VulDB Data Team • 12/31/2019
The vulnerability identified as CVE-2014-3519 resides within the OpenVZ containerization solution, specifically affecting the vzkernel modification of the Linux kernel version 2.6.32. This issue manifests in the open_by_handle_at function, which serves as a critical interface for file handle-based file access operations. The vulnerability operates within the context of containerized environments where security boundaries are meant to prevent unauthorized access to host resources. When the simfs filesystem is employed, the flaw creates a potential bypass mechanism that undermines the intended security model of container isolation.
The technical flaw stems from improper handling of the file_handle structure within the open_by_handle_at function implementation. This function typically operates by converting file handles into file descriptors, enabling access to files without requiring full path traversal. However, in the affected OpenVZ implementation, local container users who possess the CAP_DAC_READ_SEARCH capability can exploit this function to circumvent the container's security restrictions. The vulnerability specifically relates to how the system processes file_handle structures, allowing malicious users to manipulate these structures to gain access to files outside their designated container boundaries.
The operational impact of this vulnerability is significant for containerized environments, as it provides local users within a container with the ability to escape container boundaries and access arbitrary files on the host filesystem. This represents a direct violation of container isolation principles that form the foundation of container security models. Attackers with CAP_DAC_READ_SEARCH capabilities can leverage this flaw to access sensitive files, potentially including configuration data, user credentials, or other confidential information stored on the host system. The vulnerability essentially transforms a container's intended security boundary into a potential attack vector, undermining the trust model that containerization relies upon.
This vulnerability maps to CWE-284 Access Control and CWE-269 Privilege Management, as it involves improper access control mechanisms and privilege escalation within containerized environments. The ATT&CK framework categorizes this under T1548.005 Account Manipulation and T1059.001 Command and Scripting Interpreter, as local users can manipulate file access controls to escalate privileges and access unauthorized resources. The flaw demonstrates a critical weakness in container security implementation where the kernel-level protections fail to maintain proper isolation boundaries. Organizations using OpenVZ containers with simfs filesystems are particularly vulnerable, as the attack vector requires only local access within a container and the specific capability mentioned in the vulnerability description.
Mitigation strategies for CVE-2014-3519 focus primarily on upgrading to patched versions of the vzkernel, specifically versions 042stab090.5 and later. System administrators should also implement strict capability management, ensuring that container users do not possess unnecessary capabilities such as CAP_DAC_READ_SEARCH. Additionally, monitoring for unusual file access patterns and implementing proper filesystem permissions can help detect potential exploitation attempts. Organizations should consider restricting the use of simfs filesystem within containerized environments where this vulnerability could be exploited, and implement comprehensive container security policies that include regular security assessments of container configurations and kernel modifications.