CVE-2018-6977 in ESXi
Summary
by MITRE
VMware ESXi (6.7, 6.5, 6.0), Workstation (15.x and 14.x) and Fusion (11.x and 10.x) contain a denial-of-service vulnerability due to an infinite loop in a 3D-rendering shader. Successfully exploiting this issue may allow an attacker with normal user privileges in the guest to make the VM unresponsive, and in some cases, possibly result other VMs on the host or the host itself becoming unresponsive.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 05/23/2023
The vulnerability identified as CVE-2018-6977 represents a critical denial-of-service weakness affecting multiple VMware virtualization products including ESXi versions 6.7, 6.5, and 6.0, along with Workstation versions 15.x and 14.x, and Fusion versions 11.x and 10.x. This flaw manifests within the 3D-rendering shader implementation, where an infinite loop condition can be triggered through malicious input processing. The vulnerability stems from inadequate input validation and error handling mechanisms within the graphics processing subsystem that governs virtual machine display rendering capabilities. Attackers exploiting this weakness can manipulate the graphics pipeline to create a perpetual loop in shader execution, effectively consuming system resources and causing the targeted virtual machine to become unresponsive. The issue is particularly concerning because it requires only normal user privileges within the guest operating system to execute successfully, making it accessible to adversaries who may have limited initial access to the virtual environment. This vulnerability falls under the CWE-835 category of infinite loop or infinite recursion, which represents a fundamental flaw in program logic that can lead to system instability and resource exhaustion.
The operational impact of CVE-2018-6977 extends beyond individual virtual machine compromise to potentially affect entire host systems and multi-tenant environments. When exploited, the infinite loop in the 3D-rendering shader can cause the affected virtual machine to freeze completely, rendering it unavailable to legitimate users while consuming significant CPU cycles and memory resources. In shared hosting environments where multiple virtual machines operate on the same physical host, this vulnerability can lead to cascading failures affecting other VMs running on the same infrastructure. The resource exhaustion caused by the infinite loop may also impact the host operating system's ability to manage other virtual machines effectively, potentially causing broader system instability and performance degradation. Additionally, the vulnerability can be leveraged to create a denial-of-service condition that may persist until the affected VM is manually restarted or the host system is rebooted, making it particularly disruptive in production environments where uptime is critical. This type of vulnerability aligns with ATT&CK technique T1499.004 which involves network denial of service attacks, though in this case the attack vector is through legitimate virtual machine guest processes rather than external network traffic manipulation.
Mitigation strategies for CVE-2018-6977 should prioritize immediate patching of affected VMware products, as VMware has released updates specifically addressing this vulnerability in their respective software versions. Organizations should implement network segmentation and access controls to limit guest user privileges where possible, reducing the attack surface for potential exploitation. Monitoring systems should be configured to detect unusual resource consumption patterns that may indicate exploitation attempts, particularly in virtualized environments where 3D rendering capabilities are utilized. Security administrators should also consider disabling unnecessary 3D graphics features in virtual machines when these capabilities are not required for business operations. Additionally, implementing virtual machine resource limits and quotas can help contain the impact of exploitation attempts by preventing a single compromised VM from consuming excessive host resources. The vulnerability demonstrates the importance of proper input validation and error handling in graphics processing components, emphasizing the need for comprehensive security testing of all subsystems within virtualization platforms. Organizations should also maintain regular vulnerability assessment programs that include virtualization-specific security testing to identify similar weaknesses before they can be exploited by malicious actors. This vulnerability serves as a reminder of how seemingly isolated components within complex virtualization environments can create cascading security issues that affect entire infrastructure deployments.