CVE-2017-5667 in QEMU
Summary
by MITRE
The sdhci_sdma_transfer_multi_blocks function in hw/sd/sdhci.c in QEMU (aka Quick Emulator) allows local guest OS privileged users to cause a denial of service (out-of-bounds heap access and crash) or execute arbitrary code on the QEMU host via vectors involving the data transfer length.
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Analysis
by VulDB Data Team • 09/09/2020
The vulnerability identified as CVE-2017-5667 resides within the QEMU virtual machine emulator's SDHCI (Secure Digital Host Controller Interface) implementation, specifically in the sdhci_sdma_transfer_multi_blocks function located in hw/sd/sdhci.c. This flaw represents a critical security issue that affects the virtualization environment by enabling malicious guest operating systems to exploit memory access violations on the host system. The vulnerability manifests when local privileged users within the guest OS manipulate data transfer length parameters during SDHCI operations, creating conditions that lead to out-of-bounds heap access patterns.
The technical exploitation of this vulnerability occurs through improper validation of data transfer length parameters within the SDHCI controller emulation layer. When a guest OS attempts to perform multiple block data transfers using the SDHCI controller, the function fails to adequately validate the transfer length against available heap buffer boundaries. This validation gap allows attackers to specify transfer lengths that exceed allocated buffer sizes, resulting in heap corruption through out-of-bounds memory access. The flaw can be categorized under CWE-125 as out-of-bounds read conditions, while also exhibiting characteristics of CWE-787 as out-of-bounds write vulnerabilities.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enable arbitrary code execution on the host system. Local privilege escalation within the guest OS allows attackers to leverage this flaw to crash the QEMU process or, more critically, execute malicious code with the privileges of the QEMU host process. This represents a severe escalation of privileges from guest to host, as the virtualization layer becomes compromised and attackers can potentially access or manipulate other virtual machines running on the same host system. The attack vector specifically targets the SDMA (Secure Digital Memory Access) transfer mechanism, which is commonly used for high-speed data transfers in embedded systems and mobile devices.
From an adversarial perspective, this vulnerability aligns with ATT&CK technique T1059.001 for command and scripting interpreter, and T1068 for exploit for privilege escalation. The vulnerability can be exploited through guest-to-host privilege escalation chains where malicious code in the guest environment leverages the heap corruption to gain unauthorized access to host resources. The exploit requires local access within the guest OS but can result in complete host compromise, making it particularly dangerous in multi-tenant virtualization environments where multiple users share the same physical infrastructure.
Mitigation strategies for CVE-2017-5667 include immediate patching of QEMU versions containing the vulnerable sdhci_sdma_transfer_multi_blocks function, implementing strict input validation for data transfer parameters, and deploying memory protection mechanisms such as stack canaries and address space layout randomization. Virtualization administrators should also consider implementing network segmentation and access controls to limit potential attack surfaces, while monitoring for unusual memory access patterns or process behavior that may indicate exploitation attempts. Additionally, maintaining up-to-date virtualization security patches and conducting regular security assessments of virtual environments helps prevent exploitation of similar vulnerabilities in the SDHCI emulation layer.