CVE-2018-16847 in QEMU
Summary
by MITRE
An OOB heap buffer r/w access issue was found in the NVM Express Controller emulation in QEMU. It could occur in nvme_cmb_ops routines in nvme device. A guest user/process could use this flaw to crash the QEMU process resulting in DoS or potentially run arbitrary code with privileges of the QEMU process.
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Analysis
by VulDB Data Team • 06/04/2023
The vulnerability identified as CVE-2018-16847 represents a critical heap-based buffer overflow in QEMU's NVM Express controller emulation component. This flaw exists within the nvme_cmb_ops routines that handle communication between virtualized NVMe devices and the host system. The issue manifests as an out-of-bounds heap read and write access, which occurs when processing certain NVMe device operations within the virtualized environment. The vulnerability specifically affects QEMU versions prior to 2.12.0, making it a significant concern for virtualization environments that rely on NVMe controller emulation for high-performance storage operations.
The technical implementation of this vulnerability stems from inadequate bounds checking within the NVMe controller emulation code. When a guest operating system or process interacts with the emulated NVMe device, particularly through commands that access the Controller Memory Buffer (CMB), the system fails to validate array indices or memory access boundaries. This allows an attacker to manipulate memory locations beyond the intended buffer boundaries, potentially leading to memory corruption that can be exploited for privilege escalation. The vulnerability is classified as a heap-based buffer overflow under CWE-122, which specifically addresses insufficient checking of the size of a heap-based buffer. The flaw's impact is amplified by the fact that it occurs in the hypervisor layer, where guest users can leverage the vulnerability to compromise the host system's security posture.
The operational impact of this vulnerability extends beyond simple denial of service scenarios to include potential privilege escalation and arbitrary code execution. A malicious guest user or process can exploit this vulnerability to crash the QEMU process, resulting in a denial of service that affects all virtual machines running under that hypervisor. However, the more severe implications arise when the attacker can leverage the heap corruption to execute arbitrary code with the privileges of the QEMU process, which typically runs with elevated system privileges. This creates a significant threat vector for attackers seeking to break out of virtualized environments and gain unauthorized access to host resources. The vulnerability aligns with ATT&CK technique T1055.001 for privilege escalation through heap spraying and memory corruption attacks.
Mitigation strategies for CVE-2018-16847 primarily focus on immediate software updates and configuration hardening measures. Organizations should prioritize upgrading QEMU to version 2.12.0 or later, where the vulnerability has been patched through enhanced bounds checking and memory validation routines. Additionally, implementing strict virtual machine isolation policies, disabling unnecessary NVMe controller features, and monitoring for suspicious memory access patterns can help reduce the attack surface. System administrators should also consider implementing hypervisor-level security controls and regular vulnerability assessments to identify potential exploitation attempts. The patch addresses the root cause by introducing proper validation of memory access boundaries and ensuring that all heap operations within the nvme_cmb_ops routines are properly bounds-checked, preventing unauthorized memory access that could lead to privilege escalation or system compromise.