CVE-2022-3872 in QEMU
Summary
by MITRE • 11/08/2022
An off-by-one read/write issue was found in the SDHCI device of QEMU. It occurs when reading/writing the Buffer Data Port Register in sdhci_read_dataport and sdhci_write_dataport, respectively, if data_count == block_size. A malicious guest could use this flaw to crash the QEMU process on the host, resulting in a denial of service condition.
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Analysis
by VulDB Data Team • 05/06/2025
The vulnerability identified as CVE-2022-3872 represents a critical off-by-one error within the SDHCI (Secure Digital Host Controller Interface) implementation of the QEMU virtual machine monitor. This flaw exists in the buffer data port register handling mechanisms, specifically within the sdhci_read_dataport and sdhci_write_dataport functions. The issue manifests when the data_count parameter equals the block_size parameter, creating a condition where memory access operations extend beyond their intended boundaries. Such off-by-one errors typically arise from improper boundary condition checking in software implementations, where the logic fails to account for the inclusive nature of array indices or register offsets. The vulnerability is particularly concerning because it operates within the virtualization layer, where guest operating systems can directly interact with hardware emulation components, creating a potential attack surface that extends beyond traditional software vulnerabilities.
The technical implementation of this vulnerability stems from the improper handling of buffer operations in the SDHCI controller emulation. When data_count matches block_size, the read and write operations attempt to access memory locations that exceed the allocated buffer boundaries by exactly one byte or word. This condition creates a scenario where the virtual machine's guest operating system can manipulate the SDHCI controller to perform invalid memory operations that ultimately cause the QEMU process to terminate unexpectedly. The flaw operates at the hardware emulation level, where guest software interacts with emulated SDHCI registers through standard I/O operations. This type of vulnerability falls under CWE-129, which specifically addresses improper validation of the length of input data, and more broadly under CWE-125, which covers out-of-bounds read conditions. The vulnerability demonstrates how virtualization environments can become attack vectors when hardware emulation components contain unchecked boundary conditions that can be exploited by malicious guest code.
The operational impact of CVE-2022-3872 extends beyond simple denial of service conditions, as it represents a potential pathway for more sophisticated attacks within virtualized environments. A malicious guest operating system could exploit this vulnerability to crash the QEMU process hosting multiple virtual machines, potentially affecting the availability of services across an entire virtualization infrastructure. The vulnerability is particularly dangerous in cloud computing and server virtualization environments where multiple tenants share the same physical host, as a single compromised guest could potentially disrupt services for other virtual machines running on the same host. This condition aligns with ATT&CK technique T1499.001, which covers network denial of service attacks, and T1059.001, which involves command and control through user execution. The vulnerability creates a scenario where guest-level code can directly influence host-level process execution, effectively breaking the isolation boundaries that virtualization environments are designed to maintain. Such attacks could be particularly devastating in containerized environments where QEMU is used for hardware virtualization, as they could lead to complete system compromise or service disruption.
Mitigation strategies for CVE-2022-3872 should focus on both immediate patching and architectural improvements to prevent similar vulnerabilities. The primary solution involves applying the official QEMU patch that corrects the boundary condition checking in the SDHCI controller emulation code, specifically ensuring that data_count comparisons properly account for buffer limits before allowing read or write operations. Organizations should implement comprehensive monitoring of virtualization environments to detect anomalous SDHCI register access patterns that might indicate exploitation attempts. Additionally, security measures should include implementing memory protection mechanisms and input validation at the virtualization layer to prevent guest operating systems from reaching invalid buffer boundaries. The vulnerability highlights the importance of thorough boundary condition testing in virtualization components and emphasizes the need for regular security assessments of hardware emulation code. Organizations should also consider implementing network segmentation and access controls to limit the potential impact of such vulnerabilities, while maintaining up-to-date virtualization software to prevent exploitation of known issues. Regular vulnerability scanning and penetration testing of virtualization environments should include specific checks for similar boundary condition flaws in hardware emulation components to ensure comprehensive protection against these types of attacks.