CVE-2013-6436 in libvirt
Summary
by MITRE
The lxcDomainGetMemoryParameters method in lxc/lxc_driver.c in libvirt 1.0.5 through 1.2.0 does not properly check the status of LXC guests when reading memory tunables, which allows local users to cause a denial of service (NULL pointer dereference and libvirtd crash) via a guest in the shutdown status, as demonstrated by the "virsh memtune" command.
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Analysis
by VulDB Data Team • 01/18/2022
The vulnerability identified as CVE-2013-6436 resides within the libvirt virtualization management library, specifically affecting versions 1.0.5 through 1.2.0. This flaw manifests in the lxcDomainGetMemoryParameters method located in lxc/lxc_driver.c, where the system fails to adequately validate the operational state of LXC (Linux Containers) guests before attempting to read memory configuration parameters. The issue represents a classic null pointer dereference vulnerability that can be exploited by local attackers to disrupt the libvirtd daemon service.
The technical implementation of this vulnerability stems from insufficient state validation within the memory parameter retrieval process. When the lxcDomainGetMemoryParameters function processes requests for memory tunables, it does not properly verify whether the target LXC guest is in a valid operational state before attempting to access memory-related data structures. This oversight becomes particularly problematic when dealing with guests that are in the shutdown status, as the expected memory configuration data structures may have been deallocated or set to null, leading to a direct dereference of a null pointer during the memory parameter reading operation.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as it can result in complete service disruption for virtualization environments relying on libvirt. When exploited through the virsh memtune command, the vulnerability triggers a crash in the libvirtd daemon, effectively terminating the virtualization management service and requiring manual intervention to restore normal operations. This type of attack vector is particularly concerning in production environments where continuous availability of virtualization services is critical for business operations and system reliability.
The vulnerability aligns with CWE-476, which categorizes null pointer dereference issues as a fundamental programming error that can lead to system instability and service disruption. From an adversarial perspective, this vulnerability maps to ATT&CK technique T1499.001, which involves disruption of services through resource exhaustion or system crashes, and T1562.001, which covers denial of service via system resource manipulation. The local privilege requirement for exploitation makes this vulnerability particularly dangerous in multi-tenant environments where local access might be more readily available than remote access, potentially allowing malicious users to compromise the integrity of the entire virtualization infrastructure.
Organizations should implement immediate mitigations including upgrading to libvirt versions 1.2.1 or later where this vulnerability has been patched, implementing proper input validation mechanisms, and establishing monitoring protocols to detect unusual patterns of libvirtd service disruptions. Additionally, system administrators should consider implementing access controls to limit local user privileges and regularly audit virtualization management configurations to prevent exploitation of similar vulnerabilities in the broader system landscape.