CVE-2021-1673 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-2021-1671, CVE-2021-1700, CVE-2021-1701.
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Analysis
by VulDB Data Team • 10/09/2024
The Remote Procedure Call Runtime Remote Code Execution Vulnerability identified as CVE-2021-1673 represents a critical security flaw within the Windows operating system's RPC runtime component. This vulnerability affects multiple Windows versions including Windows 7, Windows Server 2008, Windows Server 2008 R2, Windows 8.1, Windows Server 2012, Windows Server 2012 R2, Windows 10, and Windows Server 2016. The flaw resides in the way the RPC runtime handles certain input parameters during remote procedure calls, creating an opportunity for malicious actors to execute arbitrary code on affected systems. This vulnerability specifically impacts the Windows Remote Procedure Call service which is fundamental to many network operations and system management tasks.
The technical implementation of this vulnerability stems from improper validation of input data within the RPC runtime library. When a remote procedure call is initiated with malformed parameters, the system fails to properly sanitize or validate the incoming data before processing it. This leads to a buffer overflow condition or other memory corruption issues that can be exploited to gain unauthorized code execution privileges. The vulnerability is particularly dangerous because it can be triggered remotely without requiring any authentication credentials, making it an ideal target for automated exploitation campaigns. According to CWE-121, this vulnerability maps to a buffer overflow condition where insufficient bounds checking allows attackers to overwrite adjacent memory locations, potentially leading to arbitrary code execution. The attack vector operates through the RPC endpoint mapper service which listens on specific network ports and accepts connections from remote clients.
The operational impact of CVE-2021-1673 extends far beyond simple remote code execution capabilities, as it provides attackers with a persistent foothold within network environments. Once successfully exploited, adversaries can establish backdoors, escalate privileges, and move laterally across the network infrastructure. The vulnerability's remote nature means that attackers can target systems from anywhere on the internet without requiring physical access or local network presence. This makes it particularly attractive for nation-state actors and organized cybercriminal groups who seek to maintain long-term access to targeted networks. The ATT&CK framework categorizes this vulnerability under T1073.001 for Remote Services and T1059.001 for Command and Scripting Interpreter, as attackers can leverage the RPC service to execute malicious commands and scripts. Organizations running affected systems face significant risk of data breaches, system compromise, and potential regulatory violations if this vulnerability remains unpatched.
Mitigation strategies for CVE-2021-1673 primarily focus on immediate patch deployment and network segmentation measures. Microsoft released security updates in their regular monthly patch Tuesday releases that address this vulnerability through proper input validation and memory management improvements. Organizations should prioritize patching all affected Windows systems, particularly those with exposed RPC services or running on network segments accessible from external networks. Network administrators should implement firewall rules to restrict access to RPC ports such as TCP 135 and dynamic RPC ports, limiting exposure to trusted network segments only. Additional protective measures include disabling unnecessary RPC services, implementing network monitoring to detect unusual RPC traffic patterns, and conducting regular vulnerability assessments to identify systems that may be running outdated software versions. The vulnerability's severity classification as a critical issue by multiple security vendors underscores the urgency of implementing these mitigations, as the potential for widespread compromise exists when this vulnerability is left unaddressed.