CVE-2022-26360 in Xen
Summary
by MITRE • 04/05/2022
IOMMU: RMRR (VT-d) and unity map (AMD-Vi) handling issues T[his CNA information record relates to multiple CVEs; the text explains which aspects/vulnerabilities correspond to which CVE.] Certain PCI devices in a system might be assigned Reserved Memory Regions (specified via Reserved Memory Region Reporting, "RMRR") for Intel VT-d or Unity Mapping ranges for AMD-Vi. These are typically used for platform tasks such as legacy USB emulation. Since the precise purpose of these regions is unknown, once a device associated with such a region is active, the mappings of these regions need to remain continuouly accessible by the device. This requirement has been violated. Subsequent DMA or interrupts from the device may have unpredictable behaviour, ranging from IOMMU faults to memory corruption.
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Analysis
by VulDB Data Team • 04/08/2022
The vulnerability described in CVE-2022-26360 represents a critical flaw in Intel Virtualization Technology for Directed I/O (VT-d) and AMD-Virtualization (AMD-Vi) IOMMU implementations that affects how Reserved Memory Regions (RMRR) and unity mapping ranges are handled during device assignment. This issue specifically targets the fundamental memory management mechanisms that ensure isolation between virtualized devices and host system memory, creating potential pathways for privilege escalation and system instability. The vulnerability stems from improper handling of memory region mappings that are designated for platform-specific tasks, particularly those related to legacy USB emulation and other critical system functions that require persistent access to specific memory ranges.
The technical flaw manifests when PCI devices that have been assigned RMRR regions under Intel VT-d or unity mapping ranges under AMD-Vi fail to maintain proper access to these reserved memory regions that are essential for platform operations. These memory regions are typically configured during system initialization and are supposed to remain accessible to devices that require them for their operation, particularly when those devices are actively handling DMA operations or generating interrupts. The violation occurs when the IOMMU implementation fails to maintain the necessary page table entries or memory mappings that allow these devices to access their designated regions, leading to scenarios where device operations might encounter IOMMU faults or cause memory corruption.
The operational impact of this vulnerability extends beyond simple system instability, potentially enabling sophisticated attack vectors that leverage the inconsistent memory access patterns to gain unauthorized access to system resources. When devices cannot properly access their reserved memory regions, the consequences range from complete system crashes and IOMMU fault conditions to more subtle memory corruption issues that could be exploited to bypass security boundaries. This vulnerability particularly affects virtualized environments where IOMMU is critical for maintaining isolation between guest operating systems and the host system, making it a significant concern for cloud computing platforms, containerized environments, and enterprise virtualization deployments. The unpredictability of the behavior makes this vulnerability particularly dangerous as it may not manifest consistently, allowing attackers to potentially exploit the condition in ways that are difficult to detect and prevent.
Mitigation strategies for CVE-2022-26360 should focus on updating system firmware and hypervisor implementations to properly handle RMRR and unity mapping regions, ensuring that memory mappings remain accessible to devices that require them for platform functions. System administrators should prioritize applying firmware updates from hardware vendors and ensure that hypervisor versions include patches that address the specific IOMMU handling issues. The vulnerability aligns with CWE-119, which addresses memory access violations, and represents a significant concern for ATT&CK technique T1068, which involves exploiting legitimate credentials and system privileges. Organizations should also implement monitoring solutions that can detect anomalous DMA behavior and memory access patterns that might indicate exploitation attempts, while maintaining regular vulnerability assessments to identify systems that may be affected by similar IOMMU implementation flaws.