CVE-2005-0176 in Linux
Summary
by MITRE
The shmctl function in Linux 2.6.9 and earlier allows local users to unlock the memory of other processes, which could cause sensitive memory to be swapped to disk, which could allow it to be read by other users once it has been released.
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Analysis
by VulDB Data Team • 06/05/2019
The vulnerability identified as CVE-2005-0176 represents a critical flaw in the Linux kernel's shared memory management system that affects versions 2.6.9 and earlier. This issue resides within the shmctl function which is responsible for controlling shared memory segments in the operating system. The vulnerability stems from improper handling of memory locking mechanisms that should prevent sensitive data from being swapped to disk storage. When a process attempts to unlock shared memory segments using shmctl, the kernel fails to properly verify ownership and access permissions, creating an opportunity for malicious local users to manipulate memory regions belonging to other processes. This flaw directly violates fundamental security principles of process isolation and memory protection that are essential for maintaining system integrity and confidentiality.
The technical implementation of this vulnerability exploits the kernel's memory management subsystem where shared memory segments can be locked into physical memory to prevent swapping. When the shmctl function processes requests to unlock memory segments, it does not adequately validate whether the requesting process has legitimate authorization to modify the target memory region. This oversight allows a local attacker to potentially unlock memory segments that belong to other processes, causing those memory pages to be eligible for swapping to disk storage. The underlying mechanism operates through the kernel's shared memory interface which maintains internal data structures tracking memory segment ownership and locking status. The vulnerability manifests when the kernel's memory management code fails to enforce proper access controls during the unlock operation, creating a race condition or authorization bypass that can be exploited by local users.
The operational impact of CVE-2005-0176 extends beyond simple information disclosure to potentially enable more sophisticated attacks involving memory scraping and data recovery. When sensitive memory from one process gets swapped to disk, it becomes accessible to other users who may have read access to the swap space, effectively creating a data leakage channel. This vulnerability is particularly dangerous in multi-user environments where process isolation is critical for maintaining security boundaries. The attack vector requires local access but can be leveraged to extract confidential information from other processes running on the same system. From an attack perspective, this vulnerability aligns with techniques described in the attack pattern taxonomy under the category of privilege escalation and information disclosure. The flaw represents a direct violation of the principle of least privilege and can be categorized as a weakness in the kernel's memory management security controls.
The security implications of this vulnerability can be analyzed through the lens of common weakness enumeration where it maps to CWE-264, representing permissions, privileges, and access controls. The vulnerability demonstrates a failure in proper access control enforcement within the kernel's shared memory management subsystem. Organizations affected by this vulnerability should consider immediate mitigation strategies including kernel updates to versions 2.6.10 and later where the issue has been addressed through proper validation of memory segment ownership during unlock operations. System administrators should also implement additional monitoring for unauthorized memory access patterns and consider restricting local user access to shared memory operations where possible. The remediation approach should include comprehensive system hardening measures and regular security assessments to identify similar vulnerabilities in other kernel subsystems. This vulnerability highlights the importance of proper kernel security testing and validation, particularly for critical system calls that handle memory management and process isolation. The fix implemented in later kernel versions demonstrates the necessity of thorough access control validation in kernel space operations, ensuring that privilege escalation attempts are properly prevented through robust authorization checks and proper memory management enforcement mechanisms.