CVE-2011-4600 in libvirt
Summary
by MITRE
The networkReloadIptablesRules function in network/bridge_driver.c in libvirt before 0.9.9 does not properly handle firewall rules on bridge networks when libvirtd is restarted, which might allow remote attackers to bypass intended access restrictions via a (1) DNS or (2) DHCP query.
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Analysis
by VulDB Data Team • 07/24/2022
The vulnerability described in CVE-2011-4600 resides within the libvirt virtualization management library, specifically in the network/bridge_driver.c component. This issue affects versions prior to 0.9.9 and represents a critical flaw in how firewall rules are managed during network restart operations. The problem manifests when the libvirtd daemon undergoes a restart process, creating a window of opportunity for unauthorized network access. The vulnerability specifically targets bridge network configurations where the networkReloadIptablesRules function fails to properly maintain or reapply firewall restrictions, leading to potential security breaches in virtualized environments that rely on libvirt for network management.
The technical flaw stems from improper state management during the restart process of the libvirtd service. When the daemon restarts, the networkReloadIptablesRules function does not adequately handle the preservation or reapplication of iptables firewall rules that were previously configured for bridge networks. This failure creates a temporary gap in network security where access controls are either not properly enforced or are completely bypassed. The vulnerability is particularly concerning because it allows remote attackers to exploit this window through legitimate network protocols such as DNS queries and DHCP requests, which are fundamental components of network infrastructure in virtualized environments. The flaw essentially creates a race condition where network access controls are temporarily disabled or misapplied, enabling unauthorized access to virtual network resources.
The operational impact of this vulnerability extends beyond simple network access issues, as it fundamentally compromises the security model of virtualized networks managed by libvirt. Attackers can leverage this vulnerability to gain unauthorized access to virtual machines and network resources that should be restricted based on firewall policies. The attack vectors through DNS and DHCP queries are particularly dangerous because these protocols are essential for network operation and are typically trusted by network infrastructure. This vulnerability affects any system running libvirt versions before 0.9.9 where bridge networks are configured, making it a widespread concern for virtualization administrators. The consequences include potential data breaches, unauthorized network access, and compromise of virtual machine isolation, which are fundamental security requirements in cloud and virtualized computing environments.
Mitigation strategies for CVE-2011-4600 require immediate patching of affected libvirt installations to version 0.9.9 or later, which contains the necessary fixes for proper firewall rule handling during restart operations. System administrators should also implement monitoring solutions to detect unusual network activity that might indicate exploitation attempts. Additional protective measures include implementing network segmentation, using more restrictive firewall rules, and ensuring that libvirtd restart operations are carefully managed and monitored. Organizations should conduct thorough vulnerability assessments to identify all systems running affected libvirt versions and ensure proper patch management processes are in place. The vulnerability aligns with CWE-284 Access Control Issues and can be categorized under ATT&CK technique T1071.004 Application Layer Protocol: DNS, making it a significant concern for both network security and virtualization security teams. This vulnerability underscores the importance of proper state management in security-critical systems and demonstrates how seemingly simple restart operations can create significant security gaps when not properly handled.