CVE-2022-0897 in libvirt
Summary
by MITRE • 03/25/2022
A flaw was found in the libvirt nwfilter driver. The virNWFilterObjListNumOfNWFilters method failed to acquire the `driver->nwfilters` mutex before iterating over virNWFilterObj instances. There was no protection to stop another thread from concurrently modifying the `driver->nwfilters` object. This flaw allows a malicious, unprivileged user to exploit this issue via libvirt’s API virConnectNumOfNWFilters to crash the network filter management daemon (libvirtd/virtnwfilterd).
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Analysis
by VulDB Data Team • 10/26/2024
The vulnerability identified as CVE-2022-0897 resides within the libvirt nwfilter driver component of the libvirt virtualization management library. This flaw manifests in the virNWFilterObjListNumOfNWFilters method which serves as an interface for querying the number of network filters managed by the libvirt daemon. The issue stems from inadequate thread synchronization mechanisms that are critical for maintaining data integrity in multi-threaded environments. The libvirt daemon operates with multiple threads handling concurrent API requests, making proper mutex acquisition essential for preventing race conditions and data corruption.
The technical flaw represents a classic race condition vulnerability classified under CWE-362, where the method fails to acquire the driver->nwfilters mutex before proceeding with iteration over virNWFilterObj instances. This omission creates a window of vulnerability where concurrent threads can modify the driver->nwfilters object structure while another thread attempts to read or iterate through it. The mutex acquisition is fundamental to ensuring that only one thread can access the shared resource at any given time, preventing inconsistent states and memory corruption. Without this protection, the data structures become vulnerable to simultaneous read and write operations that can result in undefined behavior.
The operational impact of this vulnerability extends beyond simple daemon crashes to potentially compromising the stability and availability of virtualized environments. Unprivileged users with access to libvirt's API can exploit this weakness by invoking the virConnectNumOfNWFilters function, which triggers the flawed code path. This creates a denial-of-service scenario where the network filter management daemon becomes unresponsive or terminates unexpectedly. The implications are particularly severe in production environments where libvirtd and virtnwfilterd services manage critical virtual machine network configurations, as such disruptions can cascade into broader system availability issues and affect multiple virtual machines simultaneously.
Mitigation strategies for CVE-2022-0897 should prioritize immediate patch application from the libvirt maintainers, as this vulnerability directly impacts the core functionality of virtualization management. System administrators should implement network segmentation to limit access to libvirt APIs to trusted users only, reducing the attack surface for unprivileged users. Additionally, monitoring should be enhanced to detect unusual patterns of API calls that might indicate exploitation attempts, particularly targeting the virConnectNumOfNWFilters function. The implementation of proper thread synchronization mechanisms including mutex acquisition before any iteration over shared data structures represents the fundamental fix required. Organizations should also consider implementing intrusion detection systems that can identify potential race condition exploitation patterns and maintain regular backups of virtual machine configurations to ensure rapid recovery from service disruptions. The vulnerability aligns with ATT&CK technique T1499.001 which covers network denial of service attacks, making it a critical concern for maintaining infrastructure resilience and operational continuity in virtualized computing environments.