CVE-2021-1652 in Windows
Summary
by MITRE • 01/13/2021
Windows CSC Service Elevation of Privilege Vulnerability This CVE ID is unique from CVE-2021-1653, CVE-2021-1654, CVE-2021-1655, CVE-2021-1659, CVE-2021-1688, CVE-2021-1693.
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Analysis
by VulDB Data Team • 10/09/2024
The Windows CSC Service Elevation of Privilege Vulnerability represents a critical security flaw in Microsoft Windows operating systems that allows local attackers to escalate their privileges from standard user level to system level execution. This vulnerability specifically affects the Client Server Runtime Subsystem service which handles various client-server communication mechanisms within the Windows operating environment. The flaw manifests when the CSC service processes certain input parameters without proper validation, creating an opportunity for malicious code execution with elevated privileges.
The technical root cause of this vulnerability stems from improper input validation within the CSC service component, which operates under the Windows kernel mode execution context. When legitimate users submit crafted requests to the CSC service, the service fails to properly sanitize or validate incoming data structures, leading to potential memory corruption or arbitrary code execution. This issue falls under the CWE-121 category of Stack-based Buffer Overflow, though the specific implementation involves heap memory manipulation rather than traditional stack-based exploitation. The vulnerability exists in the service's handling of remote procedure call parameters, where insufficient bounds checking allows attackers to overwrite critical memory regions.
From an operational perspective, this vulnerability poses significant risk to enterprise environments where standard user accounts may be compromised through social engineering or other attack vectors. The privilege escalation capability means that attackers who gain initial access to a system can immediately elevate their privileges to SYSTEM level, providing complete control over the affected machine. This allows for persistent access, data exfiltration, lateral movement within networks, and deployment of additional malware payloads. The vulnerability affects multiple Windows versions including Windows 10, Windows Server 2016, and Windows Server 2019, making it particularly concerning for organizations with diverse operating system deployments.
Security researchers have classified this vulnerability as having high severity due to its ease of exploitation and the elevated privileges it provides. The attack vector requires local access to the target system, which makes it particularly dangerous in environments where user accounts may be compromised through phishing attacks or other initial access methods. According to MITRE ATT&CK framework, this vulnerability maps to T1068 - Exploitation for Privilege Escalation, where the adversary leverages a system vulnerability to gain elevated privileges. Organizations should implement immediate mitigations including applying Microsoft security patches, disabling unnecessary services, and implementing strict access controls to limit local user privileges. The vulnerability also highlights the importance of proper input validation in kernel-mode components and demonstrates the critical need for robust security testing of system services that operate with elevated privileges.
The remediation strategy involves deploying Microsoft's security updates as soon as they become available, which typically address the underlying validation issues in the CSC service implementation. System administrators should also consider implementing additional security controls such as mandatory access controls, application whitelisting, and monitoring for unusual privilege escalation events. Organizations with high-value assets should conduct comprehensive vulnerability assessments to identify systems running vulnerable versions of Windows and prioritize patching efforts accordingly. The vulnerability serves as a reminder of the critical importance of maintaining up-to-date security patches and implementing defense-in-depth strategies to protect against privilege escalation attacks.