CVE-2021-36146 in ACRN
Summary
by MITRE • 07/03/2021
ACRN before 2.5 has a devicemodel/hw/pci/xhci.c NULL Pointer Dereference for a trb pointer.
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Analysis
by VulDB Data Team • 07/09/2021
The vulnerability identified as CVE-2021-36146 affects the ACRN hypervisor version 2.5 and earlier, specifically within the device model's USB host controller implementation. This issue resides in the pci/xhci.c file where a null pointer dereference occurs when processing transfer request blocks. The flaw represents a critical security weakness that could potentially allow malicious actors to disrupt system operations or escalate privileges within virtualized environments. The affected component is part of the USB eXtensible Host Controller Interface implementation that manages USB device communications in virtual machine environments.
The technical root cause of this vulnerability stems from inadequate input validation within the USB transfer request handling mechanism. When processing USB transfer request blocks, the system fails to properly validate that the trb (transfer request block) pointer is not null before attempting to dereference it. This null pointer dereference vulnerability allows an attacker to potentially trigger a system crash or execute arbitrary code by crafting malicious USB transfer requests. The flaw exists in the device model layer of the hypervisor, which serves as the interface between virtual machines and physical hardware resources, making it particularly dangerous in virtualized computing environments where multiple VMs share the same physical infrastructure.
The operational impact of this vulnerability extends beyond simple system instability, as it represents a potential path for privilege escalation and denial of service attacks within virtualized environments. Attackers could exploit this weakness to cause system crashes, potentially leading to complete hypervisor failure and affecting all virtual machines running on the compromised host. The vulnerability affects the integrity and availability of virtualized computing resources, which could result in significant operational disruptions for organizations relying on ACRN-based virtualization solutions. In cloud computing and edge computing environments where ACRN is commonly deployed, this vulnerability could enable attackers to compromise multiple virtual machines simultaneously, creating a cascading failure effect that impacts entire infrastructure deployments.
Mitigation strategies for CVE-2021-36146 should prioritize immediate patching of affected ACRN installations to version 2.5 or later where the null pointer dereference has been addressed. Organizations should implement network segmentation and access controls to limit USB device access to trusted users and systems only. Additionally, monitoring systems should be enhanced to detect anomalous USB activity patterns that might indicate exploitation attempts. The vulnerability aligns with CWE-476 which specifically addresses null pointer dereference issues in software implementations. From an adversarial perspective, this weakness could be categorized under ATT&CK technique T1059.007 for command and scripting interpreter usage, as exploitation might involve crafting malicious USB devices or commands that trigger the vulnerable code path. Organizations should also consider implementing virtualization-specific security controls including hypervisor hardening, regular security assessments, and maintaining up-to-date vulnerability management processes to prevent similar issues from arising in other components of their virtualization infrastructure.