CVE-2021-1671 in Windows
Summary
by MITRE • 01/13/2021
Remote Procedure Call Runtime Remote Code Execution Vulnerability This CVE ID is unique from CVE-2021-1658, CVE-2021-1660, CVE-2021-1664, CVE-2021-1666, CVE-2021-1667, CVE-2021-1673, CVE-2021-1700, CVE-2021-1701.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 10/09/2024
The CVE-2021-1671 vulnerability represents a critical remote code execution flaw within the Remote Procedure Call (RPC) runtime component of Microsoft Windows operating systems. This vulnerability specifically affects the handling of certain RPC requests and provides attackers with the capability to execute arbitrary code on vulnerable systems without requiring authentication. The flaw exists in the Windows RPC runtime library which is responsible for facilitating communication between different processes and applications across network boundaries. According to the Common Weakness Enumeration framework, this vulnerability maps to CWE-121, which describes heap-based buffer overflow conditions that can lead to arbitrary code execution. The vulnerability is particularly dangerous because it operates at the kernel level within the RPC infrastructure, making it an attractive target for attackers seeking persistent access to compromised systems.
The technical implementation of this vulnerability stems from improper validation of input parameters within the RPC runtime processing functions. When a specially crafted RPC request is received by a vulnerable Windows system, the malformed data can cause buffer overflows or memory corruption within the RPC service components. This memory corruption allows attackers to manipulate execution flow and ultimately execute malicious code with the privileges of the target system. The vulnerability is particularly concerning because it can be exploited through network-based attacks without requiring any user interaction or authentication credentials. Attackers can leverage this flaw to gain full system compromise, establish backdoors, or deploy additional malware payloads. The RPC runtime service typically operates on well-known ports such as TCP 135 and dynamic ports in the 1024-5000 range, making it accessible to attackers who can scan for vulnerable systems.
The operational impact of CVE-2021-1671 extends far beyond individual system compromise, as it can facilitate lateral movement within networks and enable attackers to establish persistent access to enterprise environments. Organizations running vulnerable Windows systems face significant risk of data breaches, system hijacking, and potential exfiltration of sensitive information. The vulnerability affects multiple Windows versions including Windows 7, Windows Server 2008, Windows Server 2012, and various other platforms where the RPC runtime component is present. Security researchers have noted that this vulnerability can be exploited as part of larger attack campaigns, often serving as an initial access vector for more sophisticated attacks. The lack of authentication requirements makes it particularly dangerous in environments where network segmentation is not properly implemented. According to MITRE ATT&CK framework, this vulnerability aligns with techniques such as T1075 Remote Services and T1133 External Remote Services, as it enables attackers to leverage legitimate Windows services for unauthorized access.
Mitigation strategies for CVE-2021-1671 should include immediate deployment of Microsoft security patches and updates, as well as network-based protections to restrict RPC traffic where possible. Organizations should implement network segmentation to limit access to RPC ports and services, particularly in critical infrastructure environments. The vulnerability can be addressed through standard Windows Update procedures, though administrators should verify that patches are properly applied and that systems are rebooted to complete the remediation process. Additional protective measures include implementing firewall rules to block unnecessary RPC traffic, monitoring for suspicious RPC activity, and conducting regular vulnerability assessments to identify systems that may not have been updated. Security teams should also consider deploying intrusion detection systems that can identify exploitation attempts targeting this specific vulnerability. The National Institute of Standards and Technology recommends that organizations maintain current patch management procedures and implement layered security controls to protect against such critical vulnerabilities. Organizations should also conduct regular security awareness training to ensure that personnel understand the risks associated with unpatched systems and can identify potential exploitation attempts.