CVE-2020-1040 in Windows
Summary
by MITRE
A remote code execution vulnerability exists when Hyper-V RemoteFX vGPU on a host server fails to properly validate input from an authenticated user on a guest operating system, aka 'Hyper-V RemoteFX vGPU Remote Code Execution Vulnerability'. This CVE ID is unique from CVE-2020-1032, CVE-2020-1036, CVE-2020-1041, CVE-2020-1042, CVE-2020-1043.
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Analysis
by VulDB Data Team • 07/29/2025
The CVE-2020-1040 vulnerability represents a critical remote code execution flaw within Microsoft Hyper-V RemoteFX vGPU implementation that affects virtualized environments where graphics processing units are shared between host and guest operating systems. This vulnerability specifically targets the validation mechanisms within the Hyper-V RemoteFX vGPU component that facilitates graphics virtualization in Windows Server environments. The flaw exists in the way the host server processes input data from authenticated guest operating systems, creating a pathway for malicious actors to execute arbitrary code with elevated privileges on the host system. The vulnerability is particularly concerning because it leverages the trust relationship between host and guest systems, allowing an authenticated user within a guest VM to potentially compromise the entire host infrastructure.
This remote code execution vulnerability stems from inadequate input validation within the Hyper-V RemoteFX vGPU subsystem, which operates under the Common Weakness Enumeration classification of CWE-121, referring to Buffer Overflow in a Fixed-Size Buffer. The technical flaw manifests when guest operating systems transmit specially crafted graphics-related data through the vGPU interface to the host server. The host system fails to properly sanitize or validate these inputs before processing them, enabling potential buffer overflows or memory corruption conditions that can be exploited to execute malicious code. The vulnerability operates at the hypervisor level, making it particularly dangerous as it can bypass traditional operating system security controls and potentially provide attackers with direct access to underlying host resources.
The operational impact of CVE-2020-1040 extends beyond simple privilege escalation, as successful exploitation can lead to complete compromise of the host server and all virtual machines running on it. Attackers who gain access through this vulnerability can potentially establish persistent backdoors, exfiltrate sensitive data, or use the compromised host as a launch point for further attacks within the network infrastructure. The vulnerability affects systems running Windows Server 2016 and Windows Server 2019 with Hyper-V enabled, particularly those configured to use RemoteFX vGPU for graphics virtualization. Organizations with virtualized environments that utilize GPU sharing for graphics-intensive applications are at heightened risk, as this vulnerability can be exploited without requiring additional attack vectors or credentials beyond those already established within the guest operating system.
Mitigation strategies for CVE-2020-1040 should focus on immediate patch application from Microsoft, which addresses the input validation issues within the Hyper-V RemoteFX vGPU implementation. Organizations should also consider implementing network segmentation to limit access to Hyper-V hosts and disable RemoteFX vGPU functionality if not strictly required for business operations. The vulnerability aligns with several tactics in the MITRE ATT&CK framework, particularly those related to privilege escalation and persistence, as attackers can leverage this flaw to maintain long-term access to compromised systems. Security teams should also monitor for unusual network traffic patterns or unauthorized access attempts to Hyper-V management interfaces, as these may indicate exploitation attempts. Additionally, organizations should review their virtualization policies and ensure that guest operating systems have minimal required privileges to prevent escalation of compromised guest access to host-level operations.