CVE-2020-25624 in QEMU
Summary
by MITRE • 11/30/2020
hw/usb/hcd-ohci.c in QEMU 5.0.0 has a stack-based buffer over-read via values obtained from the host controller driver.
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Analysis
by VulDB Data Team • 10/26/2024
The vulnerability identified as CVE-2020-25624 resides within the Open Host Controller Interface implementation of QEMU version 5.0.0, specifically in the hw/usb/hcd-ohci.c file. This represents a critical security flaw that affects virtualized USB controller emulation within the QEMU hypervisor environment. The issue manifests as a stack-based buffer over-read condition that occurs when processing data received from host controller drivers, creating a potential pathway for arbitrary code execution or system compromise. Such vulnerabilities are particularly dangerous in virtualized environments where the hypervisor serves as a critical security boundary between guest operating systems and the underlying physical hardware.
The technical root cause of this vulnerability stems from inadequate input validation and boundary checking within the USB host controller emulation code. When QEMU processes USB traffic through the OHCI controller implementation, it fails to properly validate the size and content of data structures received from the host driver. This allows malicious input to potentially overwrite adjacent memory locations on the stack, leading to unpredictable behavior including information disclosure, denial of service, or more severe exploitation possibilities. The flaw specifically occurs during the processing of USB transfer descriptors and their associated data structures, where the code assumes certain buffer sizes without proper validation against actual received data lengths. This type of vulnerability aligns with CWE-121 Stack-based Buffer Overflow, which is classified under the broader category of buffer overflow vulnerabilities that occur when more data is written to a buffer than it can hold.
The operational impact of CVE-2020-25624 extends significantly beyond simple denial of service scenarios, as it can potentially enable privilege escalation and remote code execution within virtualized environments. Attackers who can control USB devices or manipulate USB traffic within a QEMU virtual machine environment may exploit this vulnerability to gain unauthorized access to the host system or other virtual machines running on the same hypervisor. This is particularly concerning in cloud computing environments where multiple tenants share the same physical infrastructure, as the vulnerability could potentially be leveraged to break out of virtual machine isolation boundaries. The attack surface is further expanded by the fact that USB emulation is commonly enabled in virtual machine configurations, making this vulnerability exploitable in a wide range of deployment scenarios from development environments to production cloud infrastructures.
Mitigation strategies for CVE-2020-25624 should focus on immediate patching of QEMU installations to versions that contain the necessary code fixes. Organizations should prioritize updating their QEMU deployments to versions that address this specific buffer over-read condition in the OHCI controller implementation. Additionally, implementing network segmentation and access controls to limit USB device access within virtual environments can help reduce the attack surface. Security monitoring should be enhanced to detect unusual USB traffic patterns or potential exploitation attempts. From a defensive perspective, this vulnerability demonstrates the importance of rigorous input validation in virtualization components and aligns with ATT&CK technique T1059.001 Command and Scripting Interpreter as attackers could potentially leverage such vulnerabilities to execute malicious code within compromised virtual environments. Organizations should also consider implementing virtualization-specific security controls and regularly auditing their virtual machine configurations to ensure USB device emulation is properly restricted and monitored.