CVE-2019-7282 in netkit
Summary
by MITRE
In NetKit through 0.17, rcp.c in the rcp client allows remote rsh servers to bypass intended access restrictions via the filename of . or an empty filename. The impact is modifying the permissions of the target directory on the client side. This is similar to CVE-2018-20685.
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Analysis
by VulDB Data Team • 07/04/2023
The vulnerability identified as CVE-2019-7282 affects the NetKit rcp client version 0.17 and earlier, representing a significant security flaw in remote copy functionality that undermines access control mechanisms. This issue resides within the rcp.c source file where the client fails to properly validate filename inputs received from remote rsh servers. The vulnerability specifically manifests when remote servers provide filenames consisting of a single period or empty strings, which the client interprets in a manner that bypasses intended access restrictions. This flaw creates a path for malicious actors to manipulate file permissions on the client side, effectively allowing unauthorized modification of directory permissions that should be protected by access controls.
The technical nature of this vulnerability stems from inadequate input validation and sanitization within the rcp client implementation. When the rcp client receives a filename containing only a period or an empty string from a remote server, the client's parsing logic fails to properly handle these edge cases, leading to unexpected behavior in the file system operations. This particular flaw aligns with CWE-20, which addresses improper input validation, and represents a classic case of insecure handling of special characters in file path operations. The vulnerability's impact extends beyond simple permission modification to potentially enable broader system compromise, as directory permissions control access to critical system resources and user data.
From an operational perspective, this vulnerability creates a serious risk for systems that rely on the rcp utility for remote file operations, particularly in environments where multiple users or systems interact through remote shell services. The ability to modify target directory permissions without proper authorization undermines fundamental security principles of least privilege and access control. Attackers could exploit this vulnerability to escalate their privileges, gain persistent access to sensitive directories, or create backdoors within the system. The similarity to CVE-2018-20685 indicates this represents a recurring pattern in NetKit implementations where remote file operations fail to properly validate input, suggesting deeper architectural issues in how these legacy utilities handle remote data.
The exploitation of this vulnerability requires an attacker to have access to a remote rsh server that can be used to send malicious filenames to a victim's rcp client. This typically involves compromising a remote system that has rsh services enabled or establishing a man-in-the-middle position to intercept and modify rsh communications. The attack vector aligns with techniques described in the MITRE ATT&CK framework under T1078 for valid accounts and T1566 for credential harvesting, as the vulnerability exploits legitimate remote access mechanisms to achieve unauthorized file system modifications. Organizations using NetKit rcp utilities should consider this vulnerability as part of their broader security posture assessment, particularly in environments where legacy remote access protocols remain in use.
Mitigation strategies for CVE-2019-7282 should focus on immediate patching of affected NetKit versions, ideally upgrading to version 0.18 or later where the vulnerability has been addressed. System administrators should disable or remove rcp and rsh services from systems where they are not strictly required, as these protocols are inherently insecure and have been largely superseded by more secure alternatives like SSH. Network segmentation and firewall rules should be implemented to restrict access to rsh and rcp services to only trusted networks and systems. Additionally, monitoring should be enhanced to detect unusual file permission changes or access patterns that might indicate exploitation attempts. The vulnerability highlights the importance of validating all remote inputs and implementing proper input sanitization, which should be considered a fundamental security practice in all networked applications and utilities.