CVE-2019-11487 in Linux
Summary
by MITRE
The Linux kernel before 5.1-rc5 allows page->_refcount reference count overflow, with resultant use-after-free issues, if about 140 GiB of RAM exists. This is related to fs/fuse/dev.c, fs/pipe.c, fs/splice.c, include/linux/mm.h, include/linux/pipe_fs_i.h, kernel/trace/trace.c, mm/gup.c, and mm/hugetlb.c. It can occur with FUSE requests.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 10/14/2024
The vulnerability described in CVE-2019-11487 represents a critical reference count overflow condition within the Linux kernel that can lead to use-after-free scenarios and potential privilege escalation. This flaw exists in kernel versions prior to 5.1-rc5 and specifically targets the memory management subsystem where page reference counting mechanisms fail to properly handle extremely high memory configurations. The vulnerability manifests when systems possess approximately 140 gigabytes of RAM, creating conditions where the page->_refcount field can overflow beyond its maximum representable value, leading to unpredictable behavior and security implications.
The technical implementation of this vulnerability spans multiple kernel subsystems including file system operations, memory management, and tracing mechanisms. The affected components include the fuse device driver fs/fuse/dev.c which handles FUSE requests, pipe operations fs/pipe.c and fs/splice.c that manage inter-process communication, and core memory management files such as include/linux/mm.h and mm/gup.c. Additionally, the kernel trace subsystem kernel/trace/trace.c and huge page handling mm/hugetlb.c are impacted. The root cause lies in the improper handling of reference counting operations that fail to account for the possibility of overflow when dealing with massive memory configurations, particularly when multiple concurrent operations occur across different kernel subsystems.
The operational impact of this vulnerability extends beyond simple memory corruption to potentially enable privilege escalation and system compromise. When the reference count overflow occurs, it can result in memory pages being freed prematurely while still being referenced by other kernel components, creating use-after-free conditions that attackers can exploit. This scenario is particularly dangerous in environments with substantial memory capacity where the overflow conditions are more likely to be triggered. The vulnerability can be leveraged to execute arbitrary code with kernel privileges, potentially allowing attackers to gain complete system control. The specific triggering mechanism involves FUSE requests, which makes this vulnerability particularly concerning for systems that rely heavily on FUSE-based file systems or applications.
Mitigation strategies for CVE-2019-11487 focus primarily on kernel version upgrades to 5.1-rc5 or later, which contain the necessary patches to prevent reference count overflow conditions. System administrators should prioritize updating their kernel versions as the primary defense mechanism. Additionally, monitoring systems for unusual memory patterns and implementing proper access controls can help detect potential exploitation attempts. The vulnerability aligns with CWE-190, which describes integer overflow and underflow conditions, and can be mapped to ATT&CK technique T1068, which covers local privilege escalation through kernel vulnerabilities. Organizations should also consider implementing memory integrity checks and regular security assessments to identify systems running vulnerable kernel versions and ensure proper patch management protocols are in place to prevent exploitation of this and similar memory corruption vulnerabilities.