CVE-2017-6386 in virglrenderer
Summary
by MITRE
Memory leak in the vrend_create_vertex_elements_state function in vrend_renderer.c in virglrenderer allows local guest OS users to cause a denial of service (host memory consumption) via a large number of VIRGL_OBJECT_VERTEX_ELEMENTS commands.
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Analysis
by VulDB Data Team • 09/09/2020
The vulnerability identified as CVE-2017-6386 represents a critical memory management flaw within the virglrenderer component of virtualized graphics environments. This issue manifests in the vrend_create_vertex_elements_state function located within the vrend_renderer.c source file, where inadequate memory handling permits malicious or unintended operations to accumulate memory resources without proper cleanup. The vulnerability specifically targets local guest operating system users who can exploit this weakness through repeated issuance of VIRGL_OBJECT_VERTEX_ELEMENTS commands, creating a condition that leads to progressive memory consumption on the host system.
The technical nature of this vulnerability aligns with CWE-401, which describes improper handling of memory allocation failures, and demonstrates how insufficient resource management can create persistent memory leaks within virtualized graphics subsystems. When the vrend_create_vertex_elements_state function processes multiple vertex element state commands, it fails to properly release previously allocated memory resources, causing a gradual degradation of available host memory. This memory leak occurs in the context of virtual graphics rendering where guest operating systems communicate with host graphics drivers through virglrenderer, which serves as an intermediary for 3D graphics operations in virtualized environments.
The operational impact of this vulnerability extends beyond simple resource exhaustion, creating conditions that can lead to complete system instability and denial of service scenarios. Host systems running virtualized environments become increasingly vulnerable as guest users can continuously issue vertex element commands, causing the host memory to gradually fill up until system performance degrades significantly or crashes occur entirely. This type of vulnerability is particularly dangerous in multi-tenant virtualization environments where one guest user can potentially disrupt services for other users sharing the same host infrastructure. The attack vector is relatively simple and requires only local access within the guest OS, making it accessible to users who may not possess elevated privileges but can still cause significant harm through resource exhaustion attacks.
Mitigation strategies for this vulnerability should focus on implementing proper memory management practices within the virglrenderer component, including mandatory memory cleanup procedures after vertex element state processing and establishing limits on the number of concurrent vertex element commands that can be processed. System administrators should consider implementing monitoring solutions that track memory consumption patterns in virtualized environments and establish automated alerts when memory usage exceeds predetermined thresholds. The vulnerability also highlights the importance of input validation and resource management within virtual graphics drivers, aligning with ATT&CK technique T1499.004 for resource exhaustion attacks. Regular updates to virglrenderer components and implementation of proper access controls within virtualized environments can significantly reduce the risk of exploitation. Additionally, organizations should consider implementing virtual machine resource limits and memory allocation caps to prevent any single guest from consuming excessive host resources. The vulnerability demonstrates the critical need for robust memory management practices in virtualized graphics environments and underscores the importance of maintaining up-to-date security patches to prevent exploitation of known memory leak vulnerabilities.