CVE-2018-20815 in QEMU
Summary
by MITRE
In QEMU 3.1.0, load_device_tree in device_tree.c calls the deprecated load_image function, which has a buffer overflow risk.
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Analysis
by VulDB Data Team • 10/26/2024
The vulnerability identified as CVE-2018-20815 resides within the QEMU virtualization platform version 3.1.0 where the device tree loading functionality contains a critical buffer overflow risk. This issue manifests in the load_device_tree function located within the device_tree.c source file which invokes the deprecated load_image function. The deprecated function presents inherent security weaknesses that can be exploited to execute arbitrary code or cause denial of service conditions within the virtualized environment. The buffer overflow vulnerability occurs when the function processes device tree data structures that exceed allocated memory boundaries, creating potential attack vectors for malicious actors seeking to compromise virtual machine instances.
The technical flaw stems from the reliance on legacy code patterns that lack proper bounds checking mechanisms. When load_device_tree processes device tree blobs, it passes data to load_image which does not adequately validate input lengths or enforce memory boundaries. This deprecated function architecture fails to implement modern secure coding practices such as those recommended by the CWE (Common Weakness Enumeration) standard under CWE-121, which addresses stack-based buffer overflow conditions. The vulnerability represents a classic case of unsafe memory manipulation where the system allocates a fixed-size buffer but does not verify that incoming data fits within those boundaries before copying operations occur.
The operational impact of this vulnerability extends beyond simple memory corruption, potentially allowing attackers to execute arbitrary code within the context of the QEMU process running on the host system. In virtualized environments, this could enable privilege escalation attacks where malicious code in a guest operating system might leverage the buffer overflow to gain elevated privileges on the host machine. The attack surface is particularly concerning given QEMU's widespread use in cloud computing platforms, containerization environments, and virtualization infrastructure where multiple tenants share the same physical hardware. This vulnerability directly relates to ATT&CK technique T1055.001 which covers process injection methods, as successful exploitation could enable attackers to inject malicious code into QEMU processes.
Mitigation strategies for CVE-2018-20815 should prioritize immediate patching of QEMU installations to versions that remove or replace the deprecated load_image function with secure alternatives. Organizations should implement strict input validation measures and memory boundary checks for all device tree data processing within virtualization environments. Additionally, security monitoring should be enhanced to detect anomalous memory access patterns or unexpected behavior in QEMU processes that might indicate exploitation attempts. Network segmentation and privilege separation measures should be reinforced to limit the potential damage from successful attacks, while regular security audits should verify that deprecated functions are not being used in custom virtualization configurations. The remediation process should also include comprehensive testing to ensure that device tree loading operations function correctly without the vulnerable deprecated code paths while maintaining backward compatibility with existing virtual machine configurations.