CVE-2018-6764 in libvirt
Summary
by MITRE
util/virlog.c in libvirt does not properly determine the hostname on LXC container startup, which allows local guest OS users to bypass an intended container protection mechanism and execute arbitrary commands via a crafted NSS module.
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Analysis
by VulDB Data Team • 02/08/2023
The vulnerability identified as CVE-2018-6764 resides within the libvirt virtualization management library, specifically in the util/virlog.c component that handles logging operations for LXC containers. This flaw represents a critical security issue that undermines the fundamental isolation mechanisms designed to protect containerized environments from unauthorized access. The vulnerability stems from improper hostname determination during LXC container startup processes, creating a pathway for privilege escalation that directly compromises container security boundaries.
The technical implementation of this vulnerability exploits a weakness in how libvirt processes hostname resolution when initializing LXC containers. When containers start, the system attempts to determine the hostname through Name Service Switch (NSS) mechanisms, but the virlog.c component fails to properly validate or sanitize the hostname information obtained through these services. This improper handling allows malicious NSS modules to manipulate the hostname resolution process, effectively bypassing the intended security controls that should prevent guest OS users from executing commands outside their designated container environment. The flaw operates at the intersection of container virtualization and system service resolution, creating a unique attack vector that leverages the trust relationships between different system components.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it fundamentally compromises the security model of LXC container deployments. Local users within a container can exploit this weakness to execute arbitrary commands with elevated privileges, potentially gaining access to host resources or other containers running on the same system. This represents a significant breach of container isolation principles that are essential for multi-tenant virtualization environments. The vulnerability affects systems running libvirt versions prior to 4.0.0, making it particularly concerning for organizations maintaining older virtualization infrastructure. The attack requires local access within a container environment, but once exploited, can lead to complete compromise of the underlying host system or other containerized applications.
Mitigation strategies for CVE-2018-6764 should focus on immediate patching of libvirt installations to versions 4.0.0 or later where the hostname validation has been properly implemented. Organizations should also implement network segmentation and access controls to limit local user privileges within container environments. The vulnerability aligns with CWE-20, "Improper Input Validation," and demonstrates the importance of proper sanitization of system service inputs. From an ATT&CK framework perspective, this vulnerability maps to privilege escalation techniques and could enable lateral movement within virtualized environments. System administrators should also consider implementing monitoring solutions that detect anomalous NSS module behavior and unauthorized command execution patterns. Regular security audits of virtualization environments should include checks for proper hostname resolution mechanisms and container isolation controls to prevent similar vulnerabilities from being exploited in the future.