CVE-2018-5683 in QEMU
Summary
by MITRE
The vga_draw_text function in Qemu allows local OS guest privileged users to cause a denial of service (out-of-bounds read and QEMU process crash) by leveraging improper memory address validation.
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Analysis
by VulDB Data Team • 02/02/2023
The vulnerability identified as CVE-2018-5683 resides within the QEMU virtual machine monitor's VGA text drawing functionality, specifically in the vga_draw_text function. This flaw represents a critical security issue that affects virtualized environments where guest operating systems can exploit improper memory validation mechanisms to disrupt system operations. The vulnerability is particularly concerning because it allows local privileged users within a guest OS to execute denial of service attacks against the host QEMU process, effectively compromising system availability and potentially disrupting critical virtualized infrastructure operations.
The technical root cause of this vulnerability stems from inadequate bounds checking within the vga_draw_text function, which processes text rendering operations for virtual graphics hardware. When guest operating systems attempt to draw text using VGA text mode, the function fails to properly validate memory addresses and buffer boundaries before accessing graphical memory regions. This improper validation creates opportunities for out-of-bounds memory reads that can trigger segmentation faults and subsequent process crashes. The vulnerability is classified as a buffer overflow condition under CWE-121, specifically manifesting as an out-of-bounds read that can be exploited to cause arbitrary code execution or system instability.
The operational impact of CVE-2018-5683 extends beyond simple service disruption, as it enables attackers to potentially compromise the stability of virtualized environments that rely heavily on QEMU for hosting multiple guest operating systems. In cloud computing and data center environments where virtualization is fundamental to infrastructure operations, this vulnerability could allow malicious users to cause cascading failures across multiple virtual machines. The attack vector is particularly dangerous because it requires only local privileged access within a guest OS, making it accessible to users who have already gained some level of system compromise. This vulnerability aligns with ATT&CK technique T1499.001, which involves network denial of service attacks, though in this case the attack is executed within the virtualized environment itself.
Mitigation strategies for this vulnerability should focus on immediate patching of QEMU installations to address the memory validation flaws in the vga_draw_text function. System administrators must ensure that all virtualized environments are updated to versions that contain the appropriate bounds checking mechanisms and memory validation routines. Additionally, implementing proper isolation mechanisms between guest operating systems and the host hypervisor can help contain the impact of such vulnerabilities. Organizations should also consider deploying monitoring solutions that can detect unusual memory access patterns or process crashes that might indicate exploitation attempts. The vulnerability demonstrates the importance of robust input validation in virtualization software, particularly in graphics rendering components where memory management is critical for system stability and security.