CVE-2017-7980 in QEMU
Summary
by MITRE
Heap-based buffer overflow in Cirrus CLGD 54xx VGA Emulator in Quick Emulator (Qemu) 2.8 and earlier allows local guest OS users to execute arbitrary code or cause a denial of service (crash) via vectors related to a VNC client updating its display after a VGA operation.
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Analysis
by VulDB Data Team • 12/14/2022
The vulnerability identified as CVE-2017-7980 represents a critical heap-based buffer overflow within the Cirrus CLGD 54xx VGA emulator component of QEMU version 2.8 and earlier. This flaw exists in the virtualization environment's graphics subsystem where the emulator handles VNC client display updates following VGA operations. The vulnerability specifically manifests when guest operating systems interact with the virtual graphics hardware through VNC connections, creating a scenario where malicious input can corrupt heap memory structures. The issue stems from inadequate bounds checking during the processing of display update requests, allowing attackers to write beyond allocated memory boundaries.
The technical exploitation of this vulnerability occurs through a carefully crafted sequence of VGA operations followed by VNC display updates that trigger the buffer overflow condition. When a guest OS performs VGA operations and subsequently updates its display via VNC, the emulator fails to properly validate the size or content of incoming display update data. This validation failure enables attackers to overwrite adjacent heap memory regions, potentially leading to arbitrary code execution or system crashes. The heap corruption can be leveraged to overwrite function pointers, return addresses, or other critical control data structures within the emulator's memory space.
From an operational perspective, this vulnerability presents significant risks to virtualized environments where guest operating systems may have elevated privileges or where attackers can influence the execution flow of virtual machines. The local nature of the attack means that exploitation requires access to a running guest OS, but the potential impact extends beyond individual VMs to compromise the entire host system. Attackers can leverage this vulnerability to escalate privileges within the guest environment, execute malicious code with the privileges of the QEMU process, or cause denial of service conditions that may affect multiple virtual machines running on the same host. The vulnerability particularly affects environments where VNC is enabled for remote access to virtual machines, as this is the primary mechanism through which the exploit conditions can be triggered.
Mitigation strategies for CVE-2017-7980 focus primarily on upgrading to QEMU versions 2.9 and later where the vulnerability has been patched. The fix implements proper bounds checking and input validation for display update operations within the Cirrus VGA emulator. Organizations should also consider disabling VNC access when it is not required, implementing network segmentation to limit exposure, and monitoring for suspicious VNC activity patterns. Security patches should be applied immediately to all affected systems, with particular attention to virtualization environments running legacy QEMU versions. The vulnerability aligns with CWE-121 heap-based buffer overflow weakness and can be categorized under ATT&CK technique T1059 for execution and T1499 for denial of service, representing a critical threat to virtualization security postures.