CVE-2017-5957 in virglrenderer
Summary
by MITRE
Stack-based buffer overflow in the vrend_decode_set_framebuffer_state function in vrend_decode.c in virglrenderer before 926b9b3460a48f6454d8bbe9e44313d86a65447f, as used in Quick Emulator (QEMU), allows a local guest users to cause a denial of service (application crash) via the "nr_cbufs" argument.
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Analysis
by VulDB Data Team • 09/06/2020
The vulnerability identified as CVE-2017-5957 represents a critical stack-based buffer overflow within the virglrenderer component of QEMU's graphics emulation system. This flaw exists in the vrend_decode_set_framebuffer_state function located in vrend_decode.c, specifically affecting versions prior to the commit 926b9b3460a48f6454d8bbe9e44313d86a65447f. The vulnerability stems from inadequate input validation when processing the "nr_cbufs" argument, which controls the number of color buffers in framebuffer state configuration. When a guest operating system within a QEMU virtual machine attempts to set framebuffer state with an excessively large value for nr_cbufs, the application fails to properly bounds-check this parameter before using it to allocate stack space for buffer operations.
The technical implementation of this vulnerability exploits the fundamental principle of stack memory management where the application calculates buffer size based on user-provided input without sufficient validation. The vrend_decode_set_framebuffer_state function accepts the nr_cbufs parameter and uses it directly in stack allocation calculations, creating a scenario where malicious input can cause stack memory corruption. This type of vulnerability maps directly to CWE-121 Stack-based Buffer Overflow, which specifically addresses buffer overflows occurring in stack-allocated memory regions. The flaw operates under the assumption that guest users can manipulate the graphics subsystem through QEMU's virglrenderer interface, allowing them to craft malicious framebuffer state requests that trigger the overflow condition.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enable more sophisticated attack vectors within virtualized environments. Local guest users can leverage this vulnerability to cause application crashes, leading to system instability and potential service disruption. The nature of the vulnerability means that any process running within the guest operating system that attempts to configure graphics framebuffers can trigger the overflow, making it particularly dangerous in multi-user or untrusted guest environments. The vulnerability exists within the Quick Emulator framework, which means that virtual machine administrators must consider the security implications of guest users having access to graphics operations, as this could be exploited to disrupt the entire virtualization environment.
Mitigation strategies for CVE-2017-5957 require immediate patch application to update virglrenderer to version containing the fix commit 926b9b3460a48f6454d8bbe9e44313d86a65447f or later. System administrators should also implement strict input validation measures within guest operating systems to prevent malicious framebuffer state configuration attempts. The vulnerability demonstrates the importance of proper bounds checking in graphics driver implementations and aligns with ATT&CK technique T1068, which addresses privilege escalation through exploitation of software vulnerabilities. Additionally, implementing proper memory safety controls and static analysis tools during development can help prevent similar issues in other graphics subsystems. Organizations should also consider network segmentation and access controls to limit guest user privileges and reduce the attack surface available to potential exploiters. The vulnerability highlights the critical need for comprehensive security testing of virtualization components, particularly those handling graphics and display operations, as these interfaces often represent significant attack vectors in virtualized environments.