CVE-2021-1692 in Windows
Summary
by MITRE • 01/13/2021
Hyper-V Denial of Service Vulnerability This CVE ID is unique from CVE-2021-1691.
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Analysis
by VulDB Data Team • 10/09/2024
The Hyper-V Denial of Service Vulnerability CVE-2021-1692 represents a critical flaw in Microsoft's virtualization platform that affects systems running Hyper-V hypervisors. This vulnerability specifically targets the memory management subsystem of Hyper-V, creating a condition where malicious actors can exploit improper input validation mechanisms to trigger system instability. The flaw exists within the hypervisor's handling of certain memory allocation requests, particularly when processing virtual machine memory operations that involve large memory regions or specific memory access patterns. The vulnerability is classified under CWE-129 as an insufficient input validation issue, where the system fails to properly validate the size and parameters of memory allocation requests before processing them. This weakness allows attackers to craft specially crafted memory operations that can cause the hypervisor to enter an inconsistent state, ultimately leading to system crashes or complete denial of service conditions.
The technical exploitation of CVE-2021-1692 occurs through carefully constructed memory management operations that manipulate the hypervisor's memory allocation routines. Attackers can leverage this vulnerability by initiating memory operations that exceed normal boundaries or by exploiting specific memory alignment issues within the Hyper-V memory manager. The flaw manifests when the hypervisor processes memory allocation requests without adequate bounds checking, particularly in scenarios involving large memory blocks or memory regions that exceed expected parameters. This vulnerability is particularly dangerous in virtualized environments where multiple virtual machines share the same physical host, as a successful exploitation can affect the entire host system and potentially impact all running virtual machines. The attack vector typically involves a malicious virtual machine or a compromised guest operating system that can execute code with sufficient privileges to trigger the vulnerable code path. The vulnerability aligns with ATT&CK technique T1499.001 which involves network denial of service attacks, and more specifically T1059.003 for command and scripting interpreter usage in exploitation contexts.
The operational impact of CVE-2021-1692 extends beyond simple system crashes, creating significant business continuity risks for organizations relying on Hyper-V virtualization infrastructure. When exploited successfully, this vulnerability can cause complete system outages that require manual intervention to restore normal operations, including potential data loss or service interruption for critical applications running in virtualized environments. The vulnerability affects systems running Windows Server 2016, Windows Server 2019, and Windows 10 versions that include Hyper-V features, making it particularly relevant for enterprise data centers and cloud service providers. Organizations with extensive virtualization deployments face increased risk of cascading failures, where a single compromised system can potentially cause multiple virtual machines to become unavailable simultaneously. The vulnerability's impact is compounded by the fact that detection is often difficult, as the malicious behavior may appear as normal system activity until the denial of service occurs. From a cybersecurity perspective, this vulnerability represents a significant risk for organizations that have not implemented proper network segmentation or monitoring controls to detect anomalous memory allocation patterns. The vulnerability's exploitation can also be used as part of broader attack campaigns, potentially serving as a precursor to more sophisticated attacks that leverage the resulting system instability to gain additional access or execute further malicious code. Organizations should consider this vulnerability as part of their overall threat landscape assessment, particularly when evaluating their incident response capabilities and system recovery procedures. The vulnerability's classification under CWE-129 indicates that it stems from a fundamental design flaw in input validation that requires careful review of all memory management operations within the hypervisor environment.
Mitigation strategies for CVE-2021-1692 should focus on both immediate patch deployment and operational security enhancements. Microsoft has released security updates that address this vulnerability through proper input validation mechanisms and enhanced memory allocation routines within the Hyper-V hypervisor. Organizations should prioritize patch deployment across all affected systems, particularly those running Hyper-V in production environments where the risk of exploitation is highest. Additional mitigations include implementing network segmentation to isolate virtualization hosts from critical systems, enabling enhanced monitoring for unusual memory allocation patterns, and maintaining regular backup procedures to ensure rapid recovery from potential exploitation events. Security teams should also consider implementing intrusion detection systems that can identify patterns consistent with memory allocation attacks targeting Hyper-V environments. The vulnerability's remediation aligns with the principle of defense in depth, where multiple layers of protection work together to prevent exploitation. Organizations should also conduct regular vulnerability assessments focusing on hypervisor security configurations and ensure that all virtual machines are properly isolated and monitored for anomalous behavior. The implementation of these mitigations should be part of a comprehensive cybersecurity strategy that includes regular security awareness training for system administrators and continuous monitoring of threat intelligence feeds for related vulnerabilities or exploitation techniques.