CVE-2013-7336 in libvirt
Summary
by MITRE
The qemuMigrationWaitForSpice function in qemu/qemu_migration.c in libvirt before 1.1.3 does not properly enter a monitor when performing seamless SPICE migration, which allows local users to cause a denial of service (NULL pointer dereference and libvirtd crash) by causing domblkstat to be called at the same time as the qemuMonitorGetSpiceMigrationStatus function.
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Analysis
by VulDB Data Team • 06/16/2021
The vulnerability identified as CVE-2013-7336 resides within the libvirt virtualization management library, specifically in the qemu/qemu_migration.c file where the qemuMigrationWaitForSpice function fails to properly handle monitor entry during seamless SPICE migration operations. This flaw represents a critical race condition that can be exploited by local attackers to induce a denial of service condition affecting the libvirtd daemon. The issue stems from improper synchronization mechanisms when managing concurrent access to the QEMU monitor during migration processes, creating a scenario where multiple threads attempt to access shared resources without adequate protection.
The technical exploitation of this vulnerability occurs through a carefully timed sequence where a local user can simultaneously invoke the domblkstat command alongside the qemuMonitorGetSpiceMigrationStatus function. This concurrent execution creates a race condition that results in a NULL pointer dereference within the qemuMigrationWaitForSpice function. The flaw manifests as a classic race condition vulnerability classified under CWE-362, which specifically addresses concurrent execution issues leading to security weaknesses. The improper handling of monitor access during migration operations causes the libvirtd process to crash due to the dereferencing of an uninitialized or freed pointer, effectively rendering the virtualization management service unavailable.
The operational impact of this vulnerability extends beyond simple denial of service, as it can severely disrupt virtualization environments where libvirt is used for managing multiple virtual machines. When the libvirtd daemon crashes, all virtual machine management operations cease, potentially affecting business continuity and system availability. This vulnerability particularly impacts systems running libvirt versions prior to 1.1.3, where the synchronization mechanisms were insufficient to prevent concurrent access issues during migration processes. The attack vector requires local system access, making it less severe than remote exploits but still concerning for environments where local privileges are compromised or where privilege escalation is possible.
Mitigation strategies for CVE-2013-7336 primarily involve upgrading to libvirt version 1.1.3 or later, which includes proper synchronization mechanisms to prevent the race condition. System administrators should also implement monitoring solutions to detect unusual patterns of domblkstat and migration status queries that might indicate exploitation attempts. The fix addresses the underlying CWE-362 race condition by implementing proper mutex locking mechanisms around monitor access during migration operations. Additionally, organizations should consider implementing least privilege principles to limit local user access to virtualization management interfaces and establish regular patching schedules to ensure all systems remain protected against known vulnerabilities. The ATT&CK framework categorizes this as a privilege escalation and denial of service technique, as it leverages local access to cause system-wide availability issues through careful timing of concurrent operations against the virtualization management infrastructure.