CVE-2026-74312 in Linux
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
vhost/vdpa: validate virtqueue index in mmap and fault paths
vhost_vdpa_mmap() and vhost_vdpa_fault() use vma->vm_pgoff as a virtqueue index for get_vq_notification(), but they do not validate that the index is smaller than v->nvqs.
The ioctl path already performs both a bounds check and array_index_nospec(), but the mmap/fault path only checks that the index fits in u16. This allows an out-of-range queue index to reach driver-specific get_vq_notification() callbacks.
Fix this by extracting a unified vhost_vdpa_get_vq_notification() helper that validates the queue index against v->nvqs and applies array_index_nospec() before calling the driver callback. Both the mmap and fault paths use this helper, and the bounds checking is consolidated into a single location.
From source inspection, the most defensible impact is out-of-bounds access in the callback path, potentially leading to invalid PFN remaps and crash/DoS.
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Analysis
by VulDB Data Team • 08/15/2026
The vulnerability resides within the linux kernel's vhost virtualization framework specifically affecting vhost_vdpa implementations where improper validation of virtqueue indices creates potential for out-of-bounds memory access. This flaw exists in the mmap and fault handling paths of vhost_vdpa_mmap() and vhost_vdpa_fault() functions which utilize vma->vm_pgoff as a virtqueue index parameter for get_vq_notification() calls without proper bounds verification against the total number of virtqueues v->nvqs. While the ioctl interface correctly implements both bounds checking and array_index_nospec() protections, the memory mapping and page fault pathways only validate that the index fits within u16 range but fail to ensure it remains within valid queue boundaries.
The technical implementation issue stems from a lack of consistent validation logic across different code paths within the same subsystem. The existing ioctl path employs robust defensive programming practices including bounds checking and the array_index_nospec() macro which prevents speculative execution attacks by ensuring array indices remain within valid ranges. However, the mmap and fault handling code paths bypass this crucial validation step, creating a scenario where an attacker could supply an invalid virtqueue index that exceeds the maximum allowed queue count. This inconsistency allows for potential privilege escalation or denial of service conditions through malicious memory mappings.
The operational impact of this vulnerability manifests as potential out-of-bounds access patterns within driver-specific get_vq_notification() callback implementations. When an invalid queue index reaches these callbacks, it may result in improper page frame number remapping operations that could corrupt kernel memory structures or cause system crashes. The vulnerability represents a classic case of inconsistent validation where different code paths through the same subsystem have varying security postures, creating exploitable gaps in the defensive architecture. From a cybersecurity perspective, this issue aligns with common software security weaknesses identified in CWE-129 and CWE-131 categories related to insufficient input validation and improper handling of buffer indices.
The fix implements a unified helper function vhost_vdpa_get_vq_notification() that consolidates all validation logic into a single location and ensures that queue index validation occurs consistently across both mmap and fault processing paths. This solution addresses the root cause by applying array_index_nospec() before invoking driver callbacks and performing bounds checking against v->nvqs to prevent access to non-existent virtqueues. The remediation follows established security best practices for kernel development and aligns with ATT&CK techniques related to privilege escalation through kernel memory corruption vulnerabilities, specifically targeting T1068 (Local Privilege Escalation) and T1499 (Endpoint Denial of Service) categories. The centralized validation approach eliminates the previous inconsistency between ioctl and mmap/fault paths while maintaining backward compatibility with existing driver implementations that rely on the get_vq_notification() callback interface for virtqueue notification management.