CVE-2021-3607 in QEMU
Summary
by MITRE • 02/24/2022
An integer overflow was found in the QEMU implementation of VMWare's paravirtual RDMA device in versions prior to 6.1.0. The issue occurs while handling a "PVRDMA_REG_DSRHIGH" write from the guest due to improper input validation. This flaw allows a privileged guest user to make QEMU allocate a large amount of memory, resulting in a denial of service. The highest threat from this vulnerability is to system availability.
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Analysis
by VulDB Data Team • 10/26/2024
The vulnerability identified as CVE-2021-3607 represents a critical integer overflow flaw within QEMU's implementation of VMware's paravirtual RDMA device, affecting versions prior to 6.1.0. This issue manifests specifically when processing write operations to the "PVRDMA_REG_DSRHIGH" register from a guest operating system, creating a scenario where malicious input can trigger unexpected memory allocation behaviors. The vulnerability resides in the hypervisor's handling of paravirtualized RDMA device operations, which are designed to enable high-performance network communication between guest virtual machines and the host system. The integer overflow occurs due to inadequate input validation mechanisms that fail to properly sanitize or constrain the values submitted by the guest during device register operations.
The technical exploitation of this vulnerability leverages a privilege escalation path where a malicious guest user can manipulate the PVRDMA_REG_DSRHIGH register to cause QEMU to allocate excessive memory resources. This occurs because the hypervisor's memory allocation routines do not properly validate the size parameters derived from guest-controlled inputs, allowing an attacker to specify values that, when processed, result in integer overflow conditions. The overflow leads to the allocation of an unexpectedly large memory block, which can quickly consume available system resources and ultimately cause the QEMU process to exhaust memory resources, resulting in a denial of service condition that affects the entire virtualization environment. This flaw directly impacts the availability of virtualized services and can be exploited to disrupt critical virtual machine operations.
From an operational impact perspective, this vulnerability poses significant threats to system availability and service continuity within virtualized environments. The denial of service condition can affect not only the specific virtual machine targeted by the attack but potentially impact the entire hypervisor host, as memory exhaustion can cause cascading failures throughout the virtualization infrastructure. The vulnerability is particularly concerning in cloud computing and data center environments where multiple virtual machines share the same hypervisor resources, as a single malicious guest could potentially disrupt services for other tenants. The flaw requires minimal privileges to exploit, as it only requires access to a privileged guest user account, making it accessible to attackers who have achieved basic guest-level compromise. The vulnerability's impact aligns with CWE-190, which describes integer overflow conditions, and can be mapped to ATT&CK technique T1499.001 for disruption of availability through resource exhaustion attacks.
The recommended mitigations for CVE-2021-3607 involve immediate deployment of QEMU version 6.1.0 or later, which includes patches specifically addressing the integer overflow condition in the paravirtual RDMA device implementation. Organizations should also implement monitoring and alerting mechanisms to detect unusual memory allocation patterns that might indicate exploitation attempts. Additionally, virtualization administrators should consider disabling paravirtual RDMA devices when they are not actively required, reducing the attack surface for this particular vulnerability. Regular vulnerability assessments and penetration testing should be conducted to identify similar issues in other hypervisor components, as integer overflows often indicate broader architectural weaknesses in input validation and memory management routines. The vulnerability serves as a reminder of the critical importance of proper input validation in hypervisor implementations and the potential for guest-level exploits to cause host-level system instability.