Linux Kernel CVE-2026-53372

Intel VT-d (Virtualization Technology for Directed I/O) is the Intel IOMMU implementation in the Linux kernel, enabling hardware-enforced DMA isolation for devices. Nested domains provide a two-level IOMMU page table hierarchy used in virtualization stacks where a hypervisor manages a parent domain and a guest manages a child domain. PASID (Process Address Space ID) extends this by enabling per-process IOMMU address spaces within a single device, commonly used with SR-IOV and VFIO device passthrough. Dirty tracking in the IOMMU context allows a hypervisor (e.g., KVM) to track which guest memory pages have been modified - a prerequisite for efficient live VM migration, since only dirtied pages need to be re-copied. The vulnerability exists because the kernel's iommu/vt-d subsystem lacks a guard preventing PASID attachment to a nested domain when the nesting parent domain already has dirty tracking configured; the attachment proceeds silently, causing the tracking mechanism to produce incomplete results. CPE: cpe:2.3:a:linux:linux:*:*:*:*:*:*:*:*. NVD has not assigned a CWE, but the root cause class is a missing validation or logic error, analogous to CWE-754 (Improper Check for Unusual or Exceptional Conditions).