CVE-2012-3497 in Xen
Summary
by MITRE
(1) TMEMC_SAVE_GET_CLIENT_WEIGHT, (2) TMEMC_SAVE_GET_CLIENT_CAP, (3) TMEMC_SAVE_GET_CLIENT_FLAGS and (4) TMEMC_SAVE_END in the Transcendent Memory (TMEM) in Xen 4.0, 4.1, and 4.2 allow local guest OS users to cause a denial of service (NULL pointer dereference or memory corruption and host crash) or possibly have other unspecified impacts via a NULL client id.
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Analysis
by VulDB Data Team • 04/12/2021
The vulnerability identified as CVE-2012-3497 affects the Transcendent Memory (TMEM) subsystem within Xen hypervisor versions 4.0, 4.1, and 4.2. This issue manifests through four specific TMEM operations including TMEMC_SAVE_GET_CLIENT_WEIGHT, TMEMC_SAVE_GET_CLIENT_CAP, TMEMC_SAVE_GET_CLIENT_FLAGS, and TMEMC_SAVE_END. The flaw represents a critical security weakness that allows local guest operating system users to exploit the hypervisor's memory management functions through improper handling of NULL client identifiers. The vulnerability resides in the TMEM implementation where the hypervisor fails to properly validate client identifiers before processing memory operations, creating a path for malicious guest users to trigger system instability.
The technical nature of this vulnerability stems from inadequate input validation within the TMEM subsystem's client management functions. When a guest OS user submits a NULL client id to any of the affected TMEM operations, the hypervisor's memory management code does not properly check for this null value before proceeding with memory operations. This leads to a NULL pointer dereference condition that can result in kernel memory corruption and ultimately cause the host system to crash. The flaw specifically aligns with CWE-476, which addresses NULL pointer dereference vulnerabilities, and represents a classic case of improper validation of input parameters within kernel-level memory management functions. The vulnerability operates at the hypervisor level, making it particularly dangerous as it can be exploited by any local user within a guest OS to compromise the integrity of the host system.
The operational impact of CVE-2012-3497 extends beyond simple denial of service to potentially enable more severe attacks depending on the system configuration and guest user privileges. Local guest users can leverage this vulnerability to cause system crashes, leading to service disruption and potential data loss. The memory corruption aspect of the vulnerability could theoretically be exploited to escalate privileges or execute arbitrary code within the hypervisor context, though the primary reported impact is denial of service. The vulnerability affects all versions of Xen 4.0, 4.1, and 4.2, making it particularly concerning for organizations running these older hypervisor versions. This vulnerability directly impacts the security posture of virtualized environments and can be categorized under ATT&CK technique T1068, which covers local privilege escalation through kernel exploits.
Mitigation strategies for CVE-2012-3497 require immediate action to update affected Xen hypervisor installations to versions that contain proper input validation for client identifiers. Organizations should prioritize patching their Xen deployments to versions 4.3 or later where this vulnerability has been addressed through enhanced validation mechanisms. System administrators should also implement monitoring for suspicious memory operations and unauthorized access attempts within virtualized environments. Additional mitigations include restricting guest user privileges, implementing proper access controls, and conducting regular security assessments of virtualized infrastructure. The vulnerability demonstrates the importance of proper input validation in kernel-level code and serves as a reminder of the critical security implications of memory management flaws in hypervisor implementations. Organizations should also consider implementing network segmentation and isolation techniques to limit the potential impact of such vulnerabilities within their virtualized environments, particularly in multi-tenant cloud deployments where guest isolation is paramount.