CVE-2020-0611 in Windows
Summary
by MITRE
A remote code execution vulnerability exists in the Windows Remote Desktop Client when a user connects to a malicious server, aka 'Remote Desktop Client Remote Code Execution Vulnerability'.
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Analysis
by VulDB Data Team • 03/21/2024
The vulnerability identified as CVE-2020-0611 represents a critical remote code execution flaw within the Windows Remote Desktop Client component that exposes users to significant security risks. This vulnerability specifically affects the RDP client functionality when establishing connections to potentially compromised servers, creating a pathway for attackers to execute arbitrary code on affected systems. The flaw exists in the client-side processing of RDP protocol communications, where insufficient input validation and memory handling mechanisms fail to properly sanitize data received from remote servers. According to CWE-125, this vulnerability stems from an out-of-bounds read condition that occurs during the parsing of RDP packets, allowing malicious actors to craft specially crafted responses that trigger memory corruption. The attack vector requires a user to initiate a connection to a malicious RDP server, making social engineering a potential prerequisite for exploitation. This vulnerability aligns with ATT&CK technique T1210 which describes exploiting weaknesses in remote services to gain unauthorized access. The Windows Remote Desktop Client is widely deployed across enterprise environments, making this vulnerability particularly dangerous as it can be leveraged to establish persistent access to corporate networks through legitimate remote access tools.
The technical implementation of this vulnerability involves a buffer overflow condition within the RDP client's packet processing routines that occurs when handling malformed RDP server responses. Attackers can exploit this by setting up a malicious RDP server that sends specially crafted packets designed to trigger the out-of-bounds memory access. The vulnerability specifically affects Windows 10 versions 1803, 1809, 1903, and 1909, as well as Windows Server 2019 and Windows Server 2016. When a vulnerable client attempts to connect to such a malicious server, the corrupted memory access can lead to arbitrary code execution with the privileges of the user running the RDP client. This represents a privilege escalation scenario that can potentially allow attackers to gain system-level access, deploy malware, or establish backdoors. The exploitation process typically involves crafting RDP packets that contain oversized data fields or malformed structures that cause the client to read beyond allocated memory boundaries. The vulnerability is particularly concerning because it can be exploited without requiring authentication to the target system, making it a zero-click attack vector.
The operational impact of CVE-2020-0611 extends beyond individual system compromise to potentially enable large-scale network infiltration and lateral movement within enterprise environments. Organizations that rely heavily on remote desktop services for business operations face significant risk exposure, as attackers can leverage this vulnerability to bypass traditional network security controls. The vulnerability's impact is amplified by the widespread use of Windows Remote Desktop services across corporate networks, where it can serve as an initial access vector for more sophisticated attacks. Security professionals must consider the potential for this vulnerability to be used in targeted campaigns against high-value targets, particularly in sectors such as finance, healthcare, and government. The vulnerability's exploitation can result in data exfiltration, system compromise, and establishment of persistent access points that allow attackers to maintain control over affected systems. Organizations may experience significant operational disruption if this vulnerability is exploited in targeted attacks, potentially leading to business continuity issues and regulatory compliance violations. The vulnerability also creates opportunities for attackers to use the compromised systems as launch points for additional attacks against internal network resources.
Mitigation strategies for CVE-2020-0611 should focus on immediate patch deployment combined with network-level controls to prevent exploitation attempts. Microsoft released security update 4549951 that addresses this vulnerability, and organizations must prioritize deployment of this patch across all affected Windows systems. Network administrators should implement strict firewall rules that limit RDP traffic to trusted sources and consider disabling RDP access from public internet addresses where possible. The principle of least privilege should be enforced by restricting RDP access to only authorized users and implementing multi-factor authentication for remote connections. Organizations should also consider implementing network segmentation to isolate critical systems from general network access and deploy intrusion detection systems that can identify suspicious RDP traffic patterns. Security monitoring should include detection of unusual RDP connection attempts and abnormal data flows that might indicate exploitation attempts. Additionally, user education programs should emphasize the importance of avoiding connections to untrusted RDP servers and recognizing potential social engineering attempts that might lead users to connect to malicious servers. Regular security assessments and vulnerability scanning should be conducted to identify any remaining vulnerable systems within the organization's infrastructure. The implementation of these controls aligns with NIST cybersecurity framework recommendations for protecting against remote access service vulnerabilities and provides defense in depth against exploitation attempts.