CVE-2017-18030 in QEMU
Summary
by MITRE
The cirrus_invalidate_region function in hw/display/cirrus_vga.c in Qemu allows local OS guest privileged users to cause a denial of service (out-of-bounds array access and QEMU process crash) via vectors related to negative pitch.
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Analysis
by VulDB Data Team • 02/02/2023
The vulnerability identified as CVE-2017-18030 resides within the QEMU virtualization platform's Cirrus Logic VGA graphics adapter implementation, specifically in the cirrus_invalidate_region function located in hw/display/cirrus_vga.c. This flaw represents a critical security issue that affects virtualized environments where guest operating systems can exploit improper input validation mechanisms. The vulnerability manifests when a privileged guest user executes code that triggers malformed graphics operations, leading to unauthorized memory access patterns that compromise the stability of the hypervisor.
The technical root cause of this vulnerability stems from inadequate bounds checking within the graphics rendering subsystem of QEMU's virtual VGA controller. When processing graphics operations with negative pitch values, the cirrus_invalidate_region function fails to properly validate the input parameters before accessing internal arrays. This allows an attacker to manipulate the graphics driver's memory access patterns, causing out-of-bounds array access that ultimately results in a segmentation fault and subsequent QEMU process crash. The flaw operates at the intersection of graphics processing and memory management, where the virtual graphics adapter's implementation does not adequately sanitize user-supplied parameters that define graphics operation parameters.
From an operational perspective, this vulnerability creates significant risk for virtualized environments as it enables a local privileged guest user to execute a denial of service attack against the entire virtual machine hosting environment. The impact extends beyond simple service disruption since QEMU process crashes can lead to complete virtual machine termination, potentially affecting multiple guest operating systems running on the same hypervisor. Attackers can leverage this vulnerability to cause persistent service degradation, making it particularly dangerous in cloud computing environments where multiple tenants share the same physical infrastructure. The vulnerability's exploitation requires only local privileged access within the guest operating system, making it accessible to users who have already gained some level of system control.
The vulnerability maps directly to CWE-129, which addresses improper validation of array index values, and represents a classic example of out-of-bounds memory access that can lead to system instability. From an ATT&CK framework perspective, this vulnerability aligns with T1499.004, which covers network denial of service attacks, and T1059.001, which involves command and scripting interpreter usage, as the exploitation requires executing specific graphics operations within the guest environment. The attack vector is particularly concerning because it can be executed without requiring elevated privileges beyond those already available to the guest user, making it a stealthy method for disrupting virtualized services. Organizations should implement immediate mitigations including QEMU version updates, guest operating system hardening, and network segmentation to limit the potential impact of this vulnerability across their virtualization infrastructure.