CVE-2014-1950 in Xen
Summary
by MITRE
Use-after-free vulnerability in the xc_cpupool_getinfo function in Xen 4.1.x through 4.3.x, when using a multithreaded toolstack, does not properly handle a failure by the xc_cpumap_alloc function, which allows local users with access to management functions to cause a denial of service (heap corruption) and possibly gain privileges via unspecified vectors.
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Analysis
by VulDB Data Team • 06/09/2021
The vulnerability identified as CVE-2014-1950 represents a critical use-after-free flaw within the Xen hypervisor architecture that affects versions 4.1.x through 4.3.x. This issue specifically manifests in the xc_cpupool_getinfo function when operating under multithreaded toolstack conditions, creating a dangerous scenario where memory management becomes compromised. The vulnerability stems from inadequate error handling mechanisms within the hypervisor's CPU pool management subsystem, where the xc_cpumap_alloc function failure is not properly addressed, leading to exploitable memory corruption conditions.
The technical exploitation of this vulnerability occurs through improper memory lifecycle management where freed memory blocks are accessed after their intended use period, creating opportunities for heap corruption that can be leveraged by malicious actors. When the xc_cpumap_alloc function fails during CPU pool information retrieval operations, the system does not properly validate or handle this failure condition, resulting in a use-after-free condition that can be triggered by local users who possess management function access privileges. This flaw operates at the hypervisor level, making it particularly dangerous as it can potentially allow privilege escalation from guest operating systems to the host hypervisor itself, though the exact vector remains unspecified in the original CVE description.
From an operational standpoint, this vulnerability poses significant risks to virtualized environments where multiple threads are managing CPU pool configurations simultaneously. The multithreaded nature of the toolstack creates race conditions and memory management conflicts that exacerbate the use-after-free scenario. Local users with appropriate access rights can exploit this weakness to either cause system crashes through heap corruption or potentially escalate privileges to achieve unauthorized control over the hypervisor. The impact extends beyond simple denial of service as the heap corruption could be leveraged to execute arbitrary code within the hypervisor context, fundamentally compromising the security isolation that virtualization environments are designed to provide.
The vulnerability aligns with CWE-416, which specifically addresses use-after-free conditions in software systems, and demonstrates characteristics consistent with ATT&CK technique T1059 for privilege escalation through hypervisor compromise. Organizations running affected Xen versions must implement immediate mitigations including upgrading to patched versions, implementing proper access controls to limit management function access, and monitoring for abnormal system behavior that might indicate exploitation attempts. The remediation process requires careful consideration of the hypervisor upgrade impact on running virtual machines and ensures that all management interfaces are properly secured to prevent unauthorized access to the vulnerable functions. Additionally, system administrators should consider implementing memory integrity checks and regular security assessments to detect potential exploitation attempts that might leverage this vulnerability for more sophisticated attacks against virtualized infrastructure.