CVE-2021-3845 in ws-scrcpy
Summary
by MITRE • 01/04/2022
ws-scrcpy is vulnerable to External Control of File Name or Path
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Analysis
by VulDB Data Team • 01/06/2022
The vulnerability identified as CVE-2021-3845 affects ws-scrcpy, a web-based Android device control tool that enables remote interaction with Android devices through web browsers. This tool leverages scrcpy functionality to provide screen mirroring and device control capabilities over web connections. The vulnerability stems from insufficient input validation and sanitization within the file path handling mechanisms, creating a critical security flaw that allows attackers to manipulate file paths through external inputs. The flaw specifically manifests when the application processes user-provided data that influences file system operations, particularly in scenarios involving screen capture or file transfer functionalities.
This vulnerability represents a classic external control of file name or path issue, which maps directly to CWE-73 and aligns with ATT&CK technique T1059.3.001 for executing commands through web interfaces. The technical flaw occurs when the ws-scrcpy application accepts user-supplied parameters that are directly incorporated into file system operations without proper validation or sanitization. Attackers can exploit this by crafting malicious input that manipulates file paths to access unauthorized files, overwrite critical system components, or execute arbitrary code through path traversal attacks. The vulnerability is particularly dangerous because it operates at the file system level, potentially allowing attackers to bypass normal access controls and gain unauthorized access to sensitive data or system resources.
The operational impact of this vulnerability extends beyond simple data exposure, as it can enable attackers to perform privilege escalation attacks and gain deeper system access. When exploited, the vulnerability allows for directory traversal attacks that could lead to arbitrary file read or write operations, potentially enabling attackers to access configuration files, user data, or even system binaries. The web-based nature of ws-scrcpy means that this vulnerability can be exploited through browser-based attacks, making it accessible to attackers with minimal technical expertise. Remote exploitation is possible through web interfaces, potentially allowing attackers to compromise devices that are connected to the internet or local networks. The vulnerability affects all versions of ws-scrcpy that do not properly validate or sanitize file path inputs, creating a persistent risk for organizations using this tool for device management or remote access operations.
Mitigation strategies for this vulnerability require immediate implementation of proper input validation and sanitization measures. Organizations should ensure that all file path inputs are properly validated against allowed character sets and that path traversal sequences are explicitly rejected. The implementation of a whitelist-based approach for file operations, combined with proper directory restrictions, can prevent attackers from manipulating file paths to access unauthorized locations. Additionally, applying the principle of least privilege to ws-scrcpy operations and implementing proper access controls can limit the potential damage from successful exploitation attempts. Regular security updates and patches should be applied immediately upon availability, and network segmentation should be implemented to reduce the attack surface. Security monitoring should include detection of suspicious file path operations and anomalous file access patterns that may indicate exploitation attempts. The vulnerability also highlights the importance of secure coding practices and input validation in web-based applications, particularly those that interact with file systems or provide remote device control capabilities.