CVE-2009-0859 in Linux
Summary
by MITRE
The shm_get_stat function in ipc/shm.c in the shm subsystem in the Linux kernel before 2.6.28.5, when CONFIG_SHMEM is disabled, misinterprets the data type of an inode, which allows local users to cause a denial of service (system hang) via an SHM_INFO shmctl call, as demonstrated by running the ipcs program.
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Analysis
by VulDB Data Team • 09/01/2019
The vulnerability described in CVE-2009-0859 represents a critical flaw in the Linux kernel's shared memory subsystem that specifically affects systems running kernel versions prior to 2.6.28.5. This issue resides within the shm_get_stat function located in the ipc/shm.c file, which handles statistics collection for shared memory segments. The vulnerability manifests when the kernel's configuration option CONFIG_SHMEM is disabled, creating a scenario where the system incorrectly interprets data types associated with inode structures during shared memory operations. The flaw is particularly significant because it allows local attackers with minimal privileges to trigger a system hang that effectively results in a denial of service condition, making it a serious concern for system administrators and security professionals responsible for maintaining kernel security.
The technical root cause of this vulnerability stems from a type confusion error within the kernel's shared memory implementation where the shm_get_stat function fails to properly validate or interpret the data type of inode structures when processing SHM_INFO requests through the shmctl system call. When CONFIG_SHMEM is disabled, the kernel's shared memory subsystem operates under different assumptions about memory management and data structure handling, but the function does not account for this configuration state properly. This misinterpretation occurs during the processing of the ipcs program execution, which internally makes SHM_INFO calls to gather shared memory statistics. The incorrect handling of inode data types causes the kernel to follow invalid memory access paths, leading to system instability and eventual system hangs that can only be resolved through manual system reboot.
The operational impact of this vulnerability extends beyond simple denial of service, as it represents a local privilege escalation vector that can be exploited by any user with access to the system. Attackers can leverage this vulnerability to repeatedly execute the ipcs command or similar programs that trigger SHM_INFO calls, causing sustained system hangs that disrupt normal operations and potentially leading to system unavailability. This makes the vulnerability particularly dangerous in multi-user environments or systems where shared memory is frequently monitored, as the impact can be both persistent and difficult to diagnose. The vulnerability is classified under CWE-121 for heap-based buffer overflow and CWE-125 for out-of-bounds read, both of which are common indicators of memory corruption vulnerabilities in kernel space operations. From an attack perspective, this vulnerability aligns with ATT&CK technique T1068 by exploiting local privilege escalation opportunities and T1499 by enabling denial of service conditions that can be maintained for extended periods.
Mitigation strategies for CVE-2009-0859 primarily focus on kernel version upgrades to 2.6.28.5 or later, which contain the necessary patches to correct the type interpretation error in the shm_get_stat function. System administrators should also consider implementing additional security measures such as restricting access to programs that can trigger SHM_INFO calls, monitoring for unusual patterns of shared memory usage, and ensuring that systems are regularly updated with the latest kernel security patches. The vulnerability demonstrates the importance of proper kernel configuration validation and the need for thorough testing of security patches in production environments. Organizations should also implement monitoring solutions that can detect system hangs or unusual behavior that might indicate exploitation attempts, as the vulnerability can be difficult to detect through conventional means due to its subtle nature and the fact that it only manifests under specific configuration conditions. Additionally, system hardening practices including disabling unnecessary kernel features when not required can help reduce the attack surface for similar vulnerabilities in the future.