CVE-2021-3545 in QEMU
Summary
by MITRE • 06/02/2021
An information disclosure vulnerability was found in the virtio vhost-user GPU device (vhost-user-gpu) of QEMU in versions up to and including 6.0. The flaw exists in virgl_cmd_get_capset_info() in contrib/vhost-user-gpu/virgl.c and could occur due to the read of uninitialized memory. A malicious guest could exploit this issue to leak memory from the host.
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Analysis
by VulDB Data Team • 10/26/2024
The vulnerability identified as CVE-2021-3545 represents a critical information disclosure flaw within the QEMU virtualization environment, specifically affecting the virtio vhost-user GPU device implementation. This issue manifests in versions of QEMU up to and including version 6.0, where the vulnerability exists within the virgl_cmd_get_capset_info() function located in the contrib/vhost-user-gpu/virgl.c source file. The flaw stems from improper memory initialization practices that create a pathway for unauthorized data exposure from the host system to guest virtual machines.
The technical nature of this vulnerability aligns with CWE-457, which describes the use of uninitialized variables, and more specifically relates to CWE-200, concerning the exposure of sensitive information. The vulnerability occurs when the vhost-user-gpu component fails to properly initialize memory structures before reading from them, creating a scenario where uninitialized memory contents are inadvertently exposed to the guest operating system. This uninitialized memory reading vulnerability allows a malicious guest to potentially extract sensitive data, configuration information, or other confidential content that resides in memory regions previously used by the host system.
From an operational perspective, this vulnerability presents a significant risk to virtualized environments where guest operating systems may be compromised or controlled by malicious actors. The impact extends beyond simple information disclosure, as the leaked memory could contain cryptographic keys, authentication credentials, or other sensitive data that could be leveraged for further attacks. The vhost-user-gpu device is commonly used in graphics-intensive virtualization scenarios, making this vulnerability particularly concerning for environments that rely on GPU acceleration and virtual desktop infrastructures. Attackers could exploit this weakness to gain insights into the host system's memory layout, potentially facilitating more sophisticated attacks such as privilege escalation or lateral movement within the virtualized environment.
The exploitation of this vulnerability requires a malicious guest operating system with access to the vhost-user-gpu device interface, which typically means the attacker must already have some level of access to the virtual machine. However, the severity lies in the fact that this information leakage can occur without requiring additional privileges or complex attack vectors beyond normal guest execution. The ATT&CK framework categorizes this vulnerability under T1005, Information Disclosure, and potentially T1059, Command and Scripting Interpreter, as it enables attackers to extract information that could be used for subsequent attack phases. Organizations utilizing QEMU virtualization platforms should prioritize patching this vulnerability, as it represents a fundamental security weakness that could compromise the integrity and confidentiality of virtualized environments.
Mitigation strategies should focus on immediate patching of affected QEMU versions, ensuring that all systems utilizing vhost-user-gpu functionality are updated to versions that properly initialize memory structures before reading from them. Additionally, network segmentation and access controls should be implemented to limit guest access to potentially vulnerable device interfaces. System administrators should also consider implementing memory monitoring solutions to detect unusual memory access patterns that might indicate exploitation attempts. The vulnerability serves as a reminder of the critical importance of proper memory management in virtualization components, particularly in device emulation layers where guest and host systems interact closely.