CVE-2026-86567 in Red Hat
Summary
by MITRE • 10/14/2026
A flaw was found in DPDK lib/vhost. The VDUSE handler fails to invalidate vring pointers when the IOTLB is invalidated, leading to use-after-unmap.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability identified within the Data Plane Development Kit (DPDK) specifically affects the virtual host library component and its interaction with the Virtual Device Userspace Emulation interface. This flaw centers on a critical memory management oversight in how guest physical addresses are mapped and unmapped during device emulation operations. When an Input/Output Translation Lookaside Buffer invalidation event occurs, indicating that certain memory mappings should be removed for security or stability reasons, the VDUSE handler fails to properly clear or invalidate the corresponding virtual ring pointers associated with those mappings. This failure creates a state where the emulated device retains references to memory regions that have been logically unmapped from the guest's perspective but may still contain stale data or point to reallocated resources in the host environment.
From a technical standpoint, this defect constitutes a use-after-unmap condition, which is a specific subclass of more general out-of-bounds access vulnerabilities. The core issue lies in the lifecycle management of memory mappings within the vhost subsystem. When an IOTLB invalidation request is processed by the hypervisor or virtualization layer to revoke access permissions for a specific guest physical address range, the corresponding entries in the host's translation structures are removed. However, because the VDUSE handler does not synchronize this action with the cleanup of the vring pointers used for communication between the guest and the emulated device, these pointers continue to reference memory locations that are no longer valid or protected under the previous access rights. This discrepancy allows the system to proceed with operations using stale pointers rather than detecting the invalidation and resetting state appropriately.
The operational impact of this vulnerability is significant, particularly in multi-tenant cloud environments where isolation between virtual machines is paramount. An attacker who has gained control within a guest operating system could potentially exploit this race condition or logic error by triggering IOTLB invalidations while maintaining active communication channels with the emulated device. By carefully crafting memory access patterns and timing requests to coincide with these invalidation events, an adversary might achieve arbitrary read or write operations on host memory that should have been inaccessible. This can lead to information disclosure of sensitive data residing in other virtual machines or even privilege escalation if the attacker can manipulate kernel structures through the emulated device interface. The lack of proper pointer invalidation effectively bypasses the intended security boundaries enforced by the IOMMU and hypervisor memory management units.
This vulnerability aligns with Common Weakness Enumeration (CWE) categories such as CWE-416, Use After Free, or more specifically CWE-825, Expired Pointer Dereference, given that the pointers remain valid in software logic but invalid regarding system security policies. In terms of attack vectors and tactics, this flaw facilitates techniques associated with ATT&CK ID T1059, Command and Scripting Interpreter, if used to execute further payloads, or more critically T1074, Data Staged, for exfiltrating data from the host environment through side channels created by improper memory handling. It also relates to CWE-284, Improper Access Control, as it undermines the access control mechanisms designed to restrict guest-to-host interactions.
Mitigation strategies must focus on ensuring strict synchronization between IOTLB invalidation events and the state of virtual ring structures within the vhost subsystem. Developers should implement immediate nullification or revalidation of vring pointers whenever an associated memory mapping is invalidated by the hypervisor. Additionally, incorporating rigorous bounds checking and validation routines before any access to these rings can prevent exploitation attempts that rely on stale references. For system administrators, applying vendor-provided patches that address this specific logic error in DPDK lib/vhost is essential. Regular updates to virtualization components ensure that such memory management flaws are corrected before they can be leveraged by malicious actors targeting cloud infrastructure or private data centers relying on high-performance networking stacks provided by DPDK.