CVE-2017-6209 in virglrenderer
Summary
by MITRE
Stack-based buffer overflow in the parse_identifier function in tgsi_text.c in the TGSI auxiliary module in the Gallium driver in virglrenderer before 0.6.0 allows local guest OS users to cause a denial of service (out-of-bounds array access and QEMU process crash) via vectors related to parsing properties.
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Analysis
by VulDB Data Team • 09/08/2020
The vulnerability identified as CVE-2017-6209 represents a critical stack-based buffer overflow within the TGSI auxiliary module of virglrenderer version 0.6.0 and earlier. This flaw exists in the parse_identifier function located in tgsi_text.c, which forms part of the Gallium driver architecture. The vulnerability specifically affects virtualized environments where guest operating systems interact with the virtual graphics hardware through QEMU's virglrenderer implementation, creating a potential attack surface for local privilege escalation and system stability compromise.
The technical implementation of this vulnerability stems from inadequate bounds checking within the parse_identifier function, which processes TGSI (Texture Graphics Shader Interface) text format representations. When parsing properties within graphics shader code, the function fails to validate array access limits, leading to stack memory corruption through buffer overflow conditions. This flaw directly maps to CWE-121 Stack-based Buffer Overflow, where insufficient validation allows attackers to write beyond allocated buffer boundaries. The vulnerability manifests when guest OS users submit specially crafted graphics shader code that triggers the parsing routine with oversized or malformed property data, causing memory corruption that ultimately leads to process termination.
The operational impact of CVE-2017-6209 extends beyond simple denial of service conditions to potentially enable more sophisticated attacks within virtualized environments. When the QEMU process crashes due to out-of-bounds array access, it results in complete system instability and service disruption for virtual machines relying on the affected graphics driver. This vulnerability particularly affects virtualized desktop environments, gaming platforms, and cloud computing infrastructures where graphics acceleration through virglrenderer is commonly implemented. The local nature of the attack means that guest operating systems with access to graphics rendering capabilities can exploit this flaw, making it particularly dangerous in multi-tenant cloud environments where guest isolation is paramount.
Mitigation strategies for this vulnerability require immediate patching of virglrenderer to version 0.6.0 or later, which contains the necessary bounds checking fixes for the parse_identifier function. System administrators should implement comprehensive monitoring for unusual QEMU process crashes and memory access patterns that may indicate exploitation attempts. Network segmentation and privilege separation measures can help limit the potential impact of successful exploitation, while regular security assessments of virtualization environments should include verification of graphics driver versions and patch status. Additionally, implementing runtime protections such as stack canaries and address space layout randomization can provide additional defense-in-depth measures against potential exploitation attempts. This vulnerability highlights the importance of thorough input validation in graphics processing libraries and demonstrates how seemingly isolated driver components can create critical security risks in complex virtualized computing environments.