CVE-2017-6355 in virglrenderer
Summary
by MITRE
Integer overflow in the vrend_create_shader function in vrend_renderer.c in virglrenderer before 0.6.0 allows local guest OS users to cause a denial of service (process crash) via crafted pkt_length and offlen values, which trigger an out-of-bounds access.
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Analysis
by VulDB Data Team • 09/05/2020
The vulnerability identified as CVE-2017-6355 represents a critical integer overflow flaw within the virglrenderer library, specifically affecting the vrend_create_shader function in vrend_renderer.c. This issue exists in versions prior to 0.6.0 and demonstrates a classic buffer management error that can be exploited by local guest operating system users to execute a denial of service attack. The vulnerability manifests when crafted pkt_length and offlen values are processed, creating conditions that lead to out-of-bounds memory access patterns. The integer overflow occurs during shader creation operations, which are fundamental components of graphics processing within virtualized environments. This flaw directly impacts the stability and reliability of virtualized graphics rendering systems, particularly those utilizing virglrenderer for hardware acceleration.
The technical implementation of this vulnerability stems from inadequate input validation within the shader creation pipeline. When the vrend_create_shader function processes incoming packet data, it fails to properly validate the pkt_length and offlen parameters before performing arithmetic operations that could result in integer overflow conditions. This overflow leads to calculated memory addresses that extend beyond the allocated buffer boundaries, triggering memory access violations. The flaw operates at the intersection of graphics virtualization and memory management, where the renderer's assumption about valid input ranges becomes compromised by maliciously crafted parameters. The vulnerability's impact is amplified by the fact that it occurs within a graphics processing context, where the renderer is expected to handle various shader types and configurations from guest operating systems.
From an operational perspective, this vulnerability creates significant risk for virtualized environments that rely on virglrenderer for graphics acceleration, particularly in cloud computing platforms and desktop virtualization solutions. Local guest users can exploit this condition to crash the rendering process, effectively causing denial of service for graphics-intensive applications running within the virtual machine. The impact extends beyond simple service disruption as it can potentially affect the entire virtual machine stability, especially in scenarios where graphics processing is critical for user experience or application functionality. The vulnerability's exploitability is relatively straightforward since it only requires local access within the guest operating system, making it accessible to any user with basic privileges within the virtualized environment. This characteristic aligns with ATT&CK technique T1499.004 for Denial of Service and represents a weakness in the software supply chain that affects virtualization infrastructure components.
The remediation strategy for CVE-2017-6355 involves updating to virglrenderer version 0.6.0 or later, where the integer overflow has been addressed through proper input validation and boundary checking mechanisms. Security practitioners should prioritize this update across all virtualized environments that utilize virglrenderer for graphics processing, particularly in cloud deployments where multiple tenants may be affected. Additional mitigation measures include implementing network segmentation to limit guest user privileges and monitoring for unusual patterns in graphics processing operations that might indicate exploitation attempts. The vulnerability demonstrates the importance of robust input validation in graphics rendering libraries and highlights the need for comprehensive security testing of virtualization components. Organizations should also consider implementing automated patch management systems to ensure timely deployment of security updates and maintain visibility into their virtualization infrastructure's security posture. This vulnerability serves as a reminder of the critical nature of memory safety in graphics virtualization systems and the potential for seemingly minor implementation flaws to create significant operational impacts.