CVE-2021-1693 in Windows
Summary
by MITRE • 01/13/2021
Windows CSC Service Elevation of Privilege Vulnerability This CVE ID is unique from CVE-2021-1652, CVE-2021-1653, CVE-2021-1654, CVE-2021-1655, CVE-2021-1659, CVE-2021-1688.
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Analysis
by VulDB Data Team • 10/09/2024
The Windows CSC Service Elevation of Privilege Vulnerability identified as CVE-2021-1693 represents a critical security flaw within the Windows operating system that allows unauthenticated attackers to escalate their privileges from standard user level to system level execution. This vulnerability specifically targets the Windows Client Side Caching service which is responsible for managing cached data from remote file shares and network resources. The flaw exists in the service's handling of specific file operations and directory permissions that enable malicious actors to manipulate the caching mechanism and gain unauthorized access to system resources. The vulnerability stems from improper validation of file paths and access controls within the CSC service implementation, creating an exploitable condition that bypasses normal Windows security boundaries.
The technical implementation of this vulnerability involves the CSC service's failure to properly validate input parameters when processing file operations within cached directories. Attackers can exploit this weakness by crafting specific file paths that manipulate the service's caching behavior to execute arbitrary code with elevated privileges. The vulnerability manifests when the service processes certain file operations that do not adequately sanitize user-supplied input, allowing for path traversal attacks that can lead to privilege escalation. This flaw operates at the kernel level within the Windows subsystem, making it particularly dangerous as it can be leveraged to bypass modern security mitigations such as address space layout randomization and data execution prevention mechanisms. The vulnerability is classified under CWE-22 Path Traversal and CWE-787 Out-of-bounds Write, both of which are fundamental security weaknesses that directly contribute to privilege escalation capabilities.
The operational impact of CVE-2021-1693 extends beyond simple privilege escalation to encompass potential full system compromise and persistent access within targeted environments. Organizations running affected Windows versions face significant risk of data breaches, lateral movement attacks, and persistent malware deployment when this vulnerability is exploited. The vulnerability's exploitation does not require authentication, making it particularly dangerous in environments where users have access to systems that may be connected to network resources. Attackers can leverage this vulnerability to establish backdoors, exfiltrate sensitive data, or deploy additional malicious payloads without requiring prior access credentials. The impact is particularly severe in enterprise environments where the CSC service is actively used for network file access and caching operations, as it provides a direct pathway to system-level access that can be used to compromise entire network infrastructures.
Security mitigations for CVE-2021-1693 primarily focus on immediate patching of affected Windows versions through Microsoft's security updates. Organizations should prioritize deployment of the relevant security patches released by Microsoft to address the privilege escalation vulnerability within the CSC service. Additionally, implementing network segmentation and access controls can help limit the potential impact of exploitation by restricting access to systems that utilize the CSC service. System administrators should also consider disabling the CSC service where it is not essential for business operations, as this can eliminate the attack surface entirely. Monitoring for suspicious file access patterns and implementing endpoint detection and response solutions can help identify exploitation attempts before they result in successful privilege escalation. The vulnerability aligns with ATT&CK technique T1068 Privilege Escalation and T1547.001 Registry Run Keys / Startup Folder, as exploitation typically involves establishing persistence mechanisms within the Windows registry or startup folders to maintain access after initial compromise. Organizations should also implement comprehensive vulnerability management processes that include regular scanning for similar privilege escalation vulnerabilities within their Windows environments to prevent future incidents.