CVE-2020-13362 in QEMU
Summary
by MITRE
In QEMU 4.2.0, megasas_lookup_frame in hw/scsi/megasas.c has an out-of-bounds read via a crafted reply_queue_head field from a guest OS user.
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Analysis
by VulDB Data Team • 10/26/2024
The vulnerability CVE-2020-13362 represents a critical out-of-bounds read flaw in QEMU version 4.2.0 that affects the megasas SCSI controller implementation. This issue resides in the hw/scsi/megasas.c source file within the megasas_lookup_frame function, where improper validation of guest-provided data leads to memory access violations. The vulnerability specifically targets the reply_queue_head field which is manipulated by guest operating system users during SCSI command processing. This flaw demonstrates a classic buffer over-read condition that can be exploited through malicious guest input, potentially leading to information disclosure or system instability.
The technical implementation of this vulnerability stems from insufficient bounds checking within the SCSI controller emulation layer. When a guest OS submits SCSI commands to the megasas controller, the reply_queue_head field contains a value that should be validated against expected queue boundaries. However, the megasas_lookup_frame function fails to properly validate this field, allowing an attacker to specify an arbitrary queue head value that exceeds the allocated buffer boundaries. This misconfiguration creates an opportunity for attackers to read memory locations beyond the intended buffer limits, potentially exposing sensitive data from the hypervisor's memory space.
From an operational perspective, this vulnerability poses significant risks to virtualized environments where QEMU serves as the underlying virtualization platform. The out-of-bounds read can be exploited by malicious guest operating systems to potentially extract confidential information from the host system's memory, including kernel data structures, cryptographic keys, or other sensitive information. The attack vector is particularly concerning because it requires only guest-level privileges, making it a serious escalation risk in multi-tenant virtualization environments. This vulnerability aligns with CWE-129, which specifically addresses improper validation of input boundaries, and represents a clear example of how hypervisor-level flaws can be exploited through guest-controlled inputs.
The impact of CVE-2020-13362 extends beyond simple information disclosure, as it can serve as a stepping stone for more sophisticated attacks within virtualized environments. Attackers can leverage this vulnerability to perform memory reconnaissance, potentially identifying useful addresses for subsequent exploitation techniques. The flaw exists in the ATT&CK framework under the Tactic of Defense Evasion, where adversaries can manipulate hypervisor components to bypass security controls. Organizations running QEMU-based virtualization platforms must consider this vulnerability as part of their broader security posture, particularly in environments where guest isolation is critical. Mitigation strategies should include immediate patching to QEMU version 4.2.1 or later, which contains the necessary bounds checking fixes, along with implementing network segmentation and monitoring for suspicious SCSI command patterns that might indicate exploitation attempts.