CVE-2026-93782 in Linux
Summary
by MITRE • 09/24/2026
In the Linux kernel, the following vulnerability has been resolved:
vhost-scsi: flush backend after device ioctls
vhost-scsi translates guest response descriptors into userspace iovecs when commands are submitted. Target-core completes those commands asynchronously, so VHOST_SET_MEM_TABLE can replace the memory table while an in-flight command still retains response iovecs translated through the old table.
If the old mapping is reused after VHOST_SET_MEM_TABLE returns, command completion can write the response to an unrelated userspace object.
Flush the vhost-scsi backend after vhost_dev_ioctl() handles a device ioctl. This waits for in-flight commands that can still use the old response iovecs before the ioctl returns.
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Analysis
by VulDB Data Team • 09/24/2026
The vulnerability identified within the Linux kernel's vhost-scsi subsystem stems from an asynchronous execution model where memory table updates are not properly synchronized with pending I/O operations. Vhost-scsi serves as a virtualization component that translates guest operating system response descriptors into userspace iovec structures to facilitate data transfer between the virtual machine and the host. When commands are submitted, these translations rely on a specific memory mapping established at the time of submission. However, because target-core completes these SCSI commands asynchronously, there exists a critical race condition window where the state of the memory table can change while an in-flight command is still processing or awaiting completion.
The core technical flaw occurs when the VHOST_SET_MEM_TABLE ioctl is invoked to update the guest's memory mapping. This operation replaces the existing memory table with a new one. If the old memory mappings are not invalidated before they are accessed, there is a risk that an in-flight command will attempt to write its response data using iovec pointers derived from the outdated memory table. Since VHOST_SET_MEM_TABLE returns immediately after updating the internal structures without waiting for pending commands to finish, the kernel may proceed with subsequent operations while old references remain active. This lack of synchronization allows a stale pointer to be dereferenced against the new or unrelated userspace objects that have since occupied the same virtual memory addresses.
The operational impact of this vulnerability is severe, primarily involving data integrity and potential security breaches through unauthorized memory writes. If an in-flight command completes after the memory table has been switched but before it is flushed, the response data will be written to a location determined by the old mapping. In many cases, these locations may correspond to unrelated userspace objects belonging to different processes or services within the host environment. This results in arbitrary write capabilities for the guest virtual machine, allowing it to corrupt memory of other applications on the host system. Such behavior can lead to information disclosure if sensitive data is overwritten and read back, privilege escalation if control flow structures are modified, or denial of service through application crashes caused by corrupted memory states.
To mitigate this risk, the resolution involves flushing the vhost-scsi backend after device ioctls handle specific commands. Specifically, the kernel now waits for all in-flight commands that might still reference the old response iovecs to complete before returning from the ioctl handler. This synchronization ensures that no stale pointers are used once the memory table has been updated or is about to be invalidated. By enforcing this wait state, the system guarantees that any pending operations finish using their original valid mappings and do not interfere with subsequent memory allocations or translations.
From a classification perspective, this vulnerability aligns with CWE-362, which describes concurrent execution issues leading to race conditions where shared resources are accessed without proper synchronization mechanisms. The asynchronous nature of target-core combined with the immediate return of VHOST_SET_MEM_TABLE creates a classic time-of-check-to-time-of-use scenario regarding memory validity. Furthermore, in terms of attack vectors and tactics, this flaw relates to ATT&CK technique T1059, specifically command and script interpretation or API abuse within virtualized environments, as it allows a guest entity to manipulate host-side resources through poorly synchronized interface calls. The fix emphasizes the necessity of strict state management and synchronization barriers when dealing with asynchronous hardware emulation tasks in kernel space to prevent cross-boundary memory corruption.