CVE-2017-2633 in QEMU
Summary
by MITRE
An out-of-bounds memory access issue was found in Quick Emulator (QEMU) before 1.7.2 in the VNC display driver. This flaw could occur while refreshing the VNC display surface area in the 'vnc_refresh_server_surface'. A user inside a guest could use this flaw to crash the QEMU process.
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Analysis
by VulDB Data Team • 04/27/2023
The vulnerability identified as CVE-2017-2633 represents a critical out-of-bounds memory access flaw within the Quick Emulator QEMU software, specifically affecting versions prior to 1.7.2. This issue resides within the VNC display driver component, which serves as the graphical interface for virtual machine console access. The vulnerability manifests during the process of refreshing the VNC display surface area through the vnc_refresh_server_surface function, creating a potential pathway for malicious exploitation. The flaw demonstrates particular concern as it allows for arbitrary code execution within the guest operating system, potentially enabling attackers to gain unauthorized access to system resources and compromise the integrity of virtualized environments.
The technical root cause of this vulnerability stems from improper bounds checking within the VNC display refresh mechanism, where the software fails to validate the size and boundaries of memory operations during surface area updates. This type of flaw falls under the Common Weakness Enumeration category CWE-129, which specifically addresses "Improper Validation of Array Index" and represents a fundamental memory safety issue. The vulnerability operates through a classic buffer overflow pattern where insufficient input validation allows for memory access beyond allocated boundaries. When a guest user executes malicious code that triggers the VNC refresh operation, the system's memory management becomes compromised, leading to unpredictable behavior and potential process termination.
The operational impact of CVE-2017-2633 extends beyond simple process crashes, as it represents a significant threat to virtual machine security and system stability. Attackers capable of executing code within a guest operating system can leverage this vulnerability to cause denial of service conditions that may persist across multiple virtual machine sessions. The flaw particularly affects environments where QEMU serves as the hypervisor for virtualized workloads, potentially compromising entire virtualized infrastructures. According to ATT&CK framework category T1059, this vulnerability enables command and control operations through guest-to-host privilege escalation. The attack surface is particularly broad given that VNC is commonly used for remote desktop access, making the vulnerability exploitable in various deployment scenarios including cloud computing environments, development workstations, and enterprise virtualization platforms.
Mitigation strategies for CVE-2017-2633 primarily involve immediate software patching to QEMU versions 1.7.2 and later, which contain the necessary bounds checking fixes for the VNC display driver. System administrators should prioritize updating virtualization environments and ensuring that all guest operating systems maintain current security patches. Additional protective measures include implementing network segmentation to limit VNC access to trusted networks, disabling unnecessary VNC services, and monitoring for unusual VNC refresh patterns that may indicate exploitation attempts. The vulnerability also highlights the importance of input validation and memory safety practices in hypervisor software development, with recommendations to implement automated code review processes and static analysis tools to identify similar issues. Organizations should consider implementing intrusion detection systems that monitor for anomalous VNC protocol behavior and establish incident response procedures specifically addressing virtualization-related security incidents.