CVE-2019-19048 in Linux
Summary
by MITRE • 01/25/2023
A memory leak in the crypto_reportstat() function in drivers/virt/vboxguest/vboxguest_utils.c in the Linux kernel before 5.3.9 allows attackers to cause a denial of service (memory consumption) by triggering copy_form_user() failures, aka CID-e0b0cb938864.
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Analysis
by VulDB Data Team • 02/23/2024
The vulnerability identified as CVE-2019-19048 represents a critical memory management flaw within the Linux kernel's virtualization subsystem, specifically affecting the VirtualBox guest driver implementation. This issue resides in the vboxguest_utils.c file within the drivers/virt/vboxguest directory, where the crypto_reportstat() function fails to properly handle memory allocation during user space data copying operations. The vulnerability manifests when the copy_from_user() function encounters failures during data transfer from user space to kernel space, leading to improper memory cleanup and subsequent resource exhaustion.
The technical exploitation of this vulnerability stems from the improper handling of memory allocation within the crypto_reportstat() function, which operates under the VirtualBox guest driver framework that facilitates communication between guest operating systems and VirtualBox hypervisor. When copy_from_user() operations fail due to invalid memory addresses or access violations, the function does not properly release previously allocated kernel memory resources, creating a memory leak condition. This flaw directly correlates with CWE-401, which categorizes memory leaks as a fundamental weakness in software design that can lead to resource exhaustion and system instability.
The operational impact of this vulnerability extends beyond simple resource consumption, as it enables attackers to systematically consume available kernel memory through repeated triggering of the affected code path. Attackers can exploit this by crafting malicious user space applications that intentionally cause copy_from_user() failures, leading to progressive memory consumption that eventually results in system denial of service. The vulnerability affects all Linux kernel versions prior to 5.3.9, making it particularly concerning given the widespread deployment of older kernel versions in enterprise environments. This memory leak can be particularly devastating in virtualized environments where multiple guest instances might simultaneously exploit the vulnerability, amplifying the denial of service impact.
The mitigation strategy for CVE-2019-19048 requires immediate kernel version upgrades to 5.3.9 or later, where the memory leak has been addressed through proper error handling and resource cleanup mechanisms. System administrators should prioritize patching affected systems, particularly those running virtualized environments where the vboxguest driver is active. Additionally, monitoring for unusual memory consumption patterns and implementing automated alerting for kernel memory usage can help detect exploitation attempts. The vulnerability demonstrates the importance of proper memory management in kernel space operations, aligning with ATT&CK technique T1499.001 which covers resource exhaustion attacks. Organizations should also consider implementing kernel module access controls and restricting user space applications from triggering potentially malicious kernel interactions to minimize exploitation surface.