CVE-2011-2512 in qemu-kvm
Summary
by MITRE
The virtio_queue_notify in qemu-kvm 0.14.0 and earlier does not properly validate the virtqueue number, which allows guest users to cause a denial of service (guest crash) and possibly execute arbitrary code via a negative number in the Queue Notify field of the Virtio Header, which bypasses a signed comparison.
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Analysis
by VulDB Data Team • 12/04/2021
The vulnerability identified as CVE-2011-2512 resides within the qemu-kvm virtualization platform version 0.14.0 and earlier, specifically affecting the virtio_queue_notify function that handles communication between guest operating systems and hypervisor devices. This flaw represents a critical security issue that stems from inadequate input validation within the virtualization layer, where the system fails to properly verify the virtqueue number parameter. The vulnerability manifests when a malicious guest user manipulates the Queue Notify field in the Virtio Header structure, specifically by providing a negative number that bypasses the intended signed comparison checks. This particular flaw falls under the CWE-129 weakness category, which encompasses improper validation of array indices and other numerical inputs that can lead to buffer overflows and arbitrary code execution.
The technical implementation of this vulnerability exploits the lack of proper bounds checking in the virtio_queue_notify function, which processes notifications from guest virtual machines regarding virtqueue operations. When a negative value is passed as the virtqueue number, the system's signed comparison mechanism is circumvented, allowing unauthorized access to memory regions that should remain protected. This improper validation creates a path for privilege escalation attacks where guest users can manipulate the hypervisor's memory management structures. The vulnerability demonstrates characteristics consistent with CWE-191, which deals with integer underflow conditions that can result in unexpected behavior and potential code execution. The attack vector operates entirely within the guest context, making it particularly dangerous as it can be exploited without requiring elevated privileges within the host system.
The operational impact of CVE-2011-2512 extends beyond simple denial of service scenarios, potentially enabling complete system compromise through arbitrary code execution. Guest users can leverage this vulnerability to crash the entire virtual machine, causing service disruption and potential data loss. More concerning is the possibility of privilege escalation that could allow attackers to execute malicious code with the privileges of the hypervisor process, effectively compromising the entire virtualization environment. This vulnerability creates a significant risk for cloud computing environments and multi-tenant systems where multiple guest operating systems share the same physical hardware. The flaw affects virtualized environments that rely on virtio device emulation, making it particularly relevant to modern virtualization platforms that implement these standardized device interfaces. Security researchers have classified this vulnerability under the ATT&CK framework as a privilege escalation technique, specifically utilizing the "Exploitation for Privilege Escalation" tactic that targets hypervisor-level vulnerabilities.
Mitigation strategies for CVE-2011-2512 require immediate patching of affected qemu-kvm installations to version 0.14.1 or later, which includes proper input validation for virtqueue numbers. System administrators should implement monitoring solutions that detect anomalous virtio header structures and negative queue notify values. The patch addresses the core validation issue by ensuring that all virtqueue numbers are properly constrained to valid ranges, preventing negative values from reaching the critical processing functions. Additional protective measures include implementing virtual machine isolation controls, enabling hypervisor security features such as Intel VT-d or AMD-Vi, and maintaining strict access controls for virtual machine management interfaces. Organizations should also consider implementing network segmentation to limit the potential attack surface and regularly audit virtualization configurations to prevent similar vulnerabilities from emerging in other components of their virtualized infrastructure. The vulnerability serves as a reminder of the critical importance of input validation in hypervisor code, particularly in security-sensitive areas that handle guest-to-host communication channels.