CVE-2026-64042 in Linux
Summary
by MITRE • 07/19/2026
In the Linux kernel, the following vulnerability has been resolved:
vfio/pci: Check BAR resources before exporting a DMABUF
A DMABUF exports access to BAR resources and, although they are requested at startup time, we need to ensure they really were reserved before exporting. Otherwise, it's possible to access unreserved resources through the export.
Add a check to the DMABUF-creation path.
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Analysis
by VulDB Data Team • 07/19/2026
The vulnerability in question affects the Linux kernel's vfio/pci subsystem where improper validation of BAR (Base Address Register) resources during DMABUF creation could lead to unauthorized access to memory regions that were not properly reserved. This flaw exists within the virtual function I/O subsystem that enables device passthrough and DMA buffer sharing between kernel drivers and user-space applications. The vulnerability stems from a missing validation check in the DMABUF export mechanism, which should verify that BAR resources have been successfully allocated before making them available for external access.
The technical implementation issue occurs when the vfio pci driver creates DMABUF objects to expose memory regions to user-space processes. During normal operation, BAR resources are requested during device initialization, but the code path that exports these resources lacks proper verification that the memory reservations were actually successful. This validation gap allows potential exploitation where an attacker could access memory regions that should have been protected or unavailable due to failed reservation attempts. The flaw represents a classic privilege escalation vector through improper resource management and access control enforcement.
The operational impact of this vulnerability extends beyond simple information disclosure to potentially enable arbitrary memory read/write operations in kernel space. When DMABUF objects are created for BAR resources, they expose memory mappings that can be accessed by user-space applications or other kernel components. If unreserved memory regions are inadvertently exposed through this mechanism, attackers could leverage the access to perform privilege escalation, read sensitive kernel data, or manipulate system state. The vulnerability is particularly concerning in virtualized environments where vfio is commonly used for device passthrough scenarios.
This weakness aligns with CWE-264, which addresses permissions, privileges, and access controls, and specifically relates to improper resource management in kernel space. The flaw also maps to ATT&CK technique T1068, which involves exploiting local privilege escalation vulnerabilities through improper system access controls. Mitigation strategies should include implementing comprehensive resource validation checks before exporting DMABUF objects, ensuring that all BAR memory reservations are verified as successful before making them available for external access. Additionally, the kernel patch should enforce stricter validation of resource allocation status and implement proper error handling for failed reservation scenarios to prevent accidental exposure of unallocated memory regions.
The fix addresses the root cause by adding explicit validation checks in the DMABUF creation pathway that verify BAR resources have been properly reserved before allowing export operations. This approach follows security-by-design principles and aligns with the principle of least privilege by ensuring only legitimately allocated memory regions are exposed to external access. The vulnerability demonstrates the critical importance of input validation and resource management in kernel space, where improper handling can lead to severe security implications across multiple attack vectors including privilege escalation and data compromise.