CVE-2026-86846 in Red Hat
Summary
by MITRE • 10/14/2026
A flaw was found in DPDK lib/vhost vhost-crypto. A guest can supply an avail-ring descriptor index that is used without bounds checking, causing an out-of-bounds write in the host vhost-crypto backend.
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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 lib/vhost component responsible for handling cryptographic operations via the vhost-crypto interface. This flaw represents a critical security deficiency in how virtualized network functions interact with the underlying host system, particularly when processing packet data through software-based encryption and decryption pipelines. The core issue stems from insufficient validation of input parameters provided by the guest operating system to the hypervisor or host-side backend process. In typical vhost architectures, communication between the guest VM and the host is managed through shared memory rings, including descriptor rings that define how buffers are allocated and processed. When a guest application submits cryptographic requests, it populates these rings with descriptors containing indices pointing to available buffer slots for processing results.
The technical flaw lies in the absence of rigorous bounds checking when the vhost-crypto backend processes the avail-ring descriptor index supplied by the guest. Instead of verifying that the provided index falls within the valid range of allocated buffers or memory regions, the host code directly utilizes this unvalidated value to determine where write operations should occur. This lack of boundary validation allows a malicious or compromised guest instance to specify an arbitrary memory address offset relative to the expected buffer structure. Consequently, when the backend attempts to store cryptographic results such as ciphertext, authentication tags, or status codes into the location indicated by the descriptor index, it performs a write operation outside the intended memory boundaries. This constitutes a classic out-of-bounds write vulnerability, which is categorized under CWE-787 in the Common Weakness Enumeration standard due to its potential for memory corruption and arbitrary code execution scenarios.
The operational impact of this vulnerability is severe because it compromises the isolation guarantees typically provided by virtualization environments. An attacker with access to a guest VM can exploit this flaw to overwrite adjacent memory structures within the host process running vhost-crypto. Depending on the specific layout of the DPDK application and the surrounding memory, such an out-of-bounds write could corrupt control flow data, overwrite function pointers, or modify critical state variables. This capability effectively allows privilege escalation from a low-privilege guest environment to full control over the host process running the cryptographic backend. In cloud computing environments where multiple tenants share physical hardware through virtualization, this vulnerability poses a significant risk of cross-tenant attacks, potentially leading to data exfiltration or denial of service against other workloads hosted on the same infrastructure.
From an offensive security perspective, this flaw aligns with techniques observed in the MITRE ATT&CK framework, particularly those related to memory corruption and exploitation for initial access or privilege escalation. Attackers could leverage this vulnerability as part of a broader attack chain involving container escape or hypervisor breakout scenarios. The exploitability depends on factors such as Address Space Layout Randomization (ASLR) protections enabled on the host system and whether other mitigations like stack canaries are active, but the fundamental lack of input validation remains a critical weakness that must be addressed to ensure secure operation of virtualized cryptographic services.
Mitigation strategies primarily involve applying vendor-provided patches that introduce strict bounds checking logic into the vhost-crypto backend code path. Developers and system administrators should verify that their DPDK installations are updated to versions where this specific input validation has been implemented. Additionally, defense-in-depth measures such as enabling hardware-assisted virtualization features like Intel VT-x or AMD-V with appropriate memory protection extensions can help limit the impact of any successful exploitation attempts by restricting direct physical memory access from guest domains. Network segmentation and strict isolation policies for VMs running cryptographic workloads further reduce the attack surface by ensuring that only trusted, audited guests have permission to interact with vhost-crypto interfaces. Regular security audits focusing on shared-memory interface implementations in virtualization stacks are recommended to identify similar validation gaps before they can be exploited in production environments.