CVE-2014-8131 in libvirt
Summary
by MITRE
The qemu implementation of virConnectGetAllDomainStats in libvirt before 1.2.11 does not properly handle locks when a domain is skipped due to ACL restrictions, which allows a remote authenticated users to cause a denial of service (deadlock or segmentation fault and crash) via a request to access the users does not have privileges to access.
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Analysis
by VulDB Data Team • 03/01/2022
The vulnerability described in CVE-2014-8131 resides within the libvirt virtualization management library, specifically affecting versions prior to 1.2.11. This flaw manifests in the qemu implementation of the virConnectGetAllDomainStats function which is responsible for retrieving statistics from all virtual domains managed by the hypervisor. The issue stems from improper lock handling mechanisms when the system encounters virtual domains that are restricted by Access Control List (ACL) policies, creating a critical race condition that can be exploited by authenticated attackers.
The technical root cause of this vulnerability lies in the inadequate synchronization mechanisms within the libvirt daemon's locking implementation. When a user requests domain statistics through the virConnectGetAllDomainStats API call, the system iterates through all available virtual domains and attempts to gather statistics for each one. However, when a domain is skipped due to ACL restrictions, the locking mechanism fails to properly release or manage the acquired locks, leading to a deadlock condition. This improper lock management can result in either a complete system deadlock where no further operations can proceed, or more commonly a segmentation fault that causes the libvirt daemon to crash and restart, effectively creating a denial of service condition.
From an operational perspective, this vulnerability represents a significant threat to virtualization infrastructure security as it allows authenticated users with limited privileges to disrupt the entire virtualization management system. The attack vector requires only a single authenticated connection to the libvirt daemon, making it particularly dangerous in multi-tenant environments where different users may have varying levels of access rights. The impact extends beyond simple service disruption, as the daemon crash can lead to loss of management capabilities and potential data inconsistency in virtualized environments that rely heavily on libvirt for domain management and monitoring.
The vulnerability aligns with CWE-664, which describes improper control of a resource through lifetime management, specifically highlighting the improper handling of locks and synchronization primitives. Additionally, this issue maps to ATT&CK technique T1499.004, which covers "Virtualization/Sandbox Evasion: Cloud API" and represents a denial of service attack that can be used to disrupt cloud infrastructure management services. Organizations using libvirt-based virtualization platforms should prioritize immediate patching to version 1.2.11 or later, where the locking mechanisms have been properly corrected to ensure that all acquired locks are appropriately released even when domain access is denied due to ACL restrictions. System administrators should also implement monitoring for unusual daemon restart patterns and consider implementing additional access controls to limit the impact of potential exploitation attempts.
The fix implemented in libvirt 1.2.11 addresses the core issue by ensuring that all locks are properly released when domain access is denied due to ACL restrictions, preventing both deadlock conditions and segmentation faults. This correction follows established best practices for concurrent programming and resource management in multi-threaded applications, particularly in systems where privilege escalation and access control are critical components of the security model. Organizations should conduct thorough testing of patched systems to ensure that the fix does not introduce any regressions in legitimate domain statistics gathering operations while maintaining the security hardening against this specific denial of service vector.