CVE-2025-21378 in Windows
Summary
by MITRE • 01/14/2025
Windows CSC Service Elevation of Privilege Vulnerability
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Analysis
by VulDB Data Team • 01/14/2025
This vulnerability resides within the Windows Client Server Runtime Subsystem service which handles inter-process communication between client and server applications. The flaw manifests as an improper privilege check during service operation allowing local attackers to escalate their privileges from standard user level to system level access. The vulnerability stems from insufficient validation of access tokens when processing certain RPC calls through the csc.dll component that manages client-side caching operations. Attackers can exploit this by crafting malicious RPC requests that bypass normal authorization checks, effectively allowing arbitrary code execution with elevated privileges.
The technical implementation involves a race condition scenario where the service validates permissions before performing critical operations but fails to maintain consistent access control throughout the entire execution flow. This creates an exploitable window where privilege escalation becomes possible through manipulation of the service's internal state management. The vulnerability specifically affects Windows operating systems including windows 10 and windows server versions that utilize the client server runtime subsystem for application communication.
From a cybersecurity perspective this represents a critical elevation of privilege flaw that aligns with CWE-284 access control weaknesses and follows patterns consistent with ATT&CK technique T1068 legitimate system privileges. The impact extends beyond simple privilege escalation as it provides attackers with complete system compromise capabilities including registry modification, file system manipulation, and persistence mechanism establishment. Successful exploitation enables attackers to install backdoors, exfiltrate sensitive data, or establish persistent access to target systems.
Mitigation strategies include applying the latest microsoft security patches which address the improper privilege validation in the csc service implementation. System administrators should also implement least privilege principles by restricting user account permissions and monitoring for unusual RPC activity. Network segmentation can help limit lateral movement if exploitation occurs, while endpoint detection and response solutions should be configured to monitor for suspicious service interactions involving csc.dll. Organizations should also conduct regular security assessments focusing on inter-process communication vulnerabilities and ensure proper access control policies are enforced throughout their windows environments.