CVE-2004-1162 in scponly
Summary
by MITRE
The unison command in scponly before 4.0 does not properly restrict programs that can be run, which could allow remote authenticated users to bypass intended access restrictions and execute arbitrary programs via the (1) -rshcmd or (2) -sshcmd flags.
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Analysis
by VulDB Data Team • 07/01/2021
The vulnerability identified as CVE-2004-1162 affects the scponly package version 4.0 and earlier, specifically targeting the unison command implementation within this restricted shell environment. This flaw represents a critical authorization bypass that undermines the fundamental security model of scponly, which is designed to provide restricted access to remote users while preventing them from executing arbitrary commands on the target system. The vulnerability stems from improper validation of command-line arguments, particularly the -rshcmd and -sshcmd flags that are intended to control which programs can be executed through the restricted shell interface.
The technical flaw manifests in the insufficient input validation mechanism that governs how the unison command processes these specific flags. When remote authenticated users provide malicious arguments through the -rshcmd or -sshcmd parameters, the system fails to properly sanitize or restrict the execution paths, allowing attackers to bypass the intended access controls. This vulnerability operates at the command execution level within the shell environment, where legitimate access restrictions are circumvented through crafted command-line inputs. The flaw is classified under CWE-78 as a failure to properly sanitize command arguments, creating a path for command injection attacks that can be exploited by authenticated users who have access to the scponly environment.
The operational impact of this vulnerability is significant as it enables authenticated remote attackers to execute arbitrary programs on the target system with the privileges of the scponly user account. This represents a complete bypass of the intended security boundaries that scponly is designed to enforce, potentially allowing attackers to escalate privileges, access restricted files, or establish persistent access to the compromised system. The vulnerability affects systems where scponly is used as a restricted shell for file transfer operations, particularly in environments where users need to perform secure file transfers but should not have full shell access. Attackers can leverage this weakness to execute commands that were never intended to be available within the restricted shell environment, effectively neutralizing the security controls that the tool was designed to provide.
Mitigation strategies for this vulnerability require immediate patching of the scponly package to version 4.0 or later, where the command-line argument validation has been properly implemented. System administrators should also implement additional monitoring and logging of command execution within restricted shell environments to detect potential exploitation attempts. The remediation process involves verifying that the -rshcmd and -sshcmd flags are properly sanitized and that only explicitly permitted programs can be executed through these interfaces. Organizations should also consider implementing additional access controls such as mandatory access controls or privilege separation mechanisms to further reduce the impact of potential exploitation. This vulnerability aligns with ATT&CK technique T1059.001 for command and scripting interpreter and T1566.001 for spearphishing attachment, as it enables attackers to execute arbitrary commands through legitimate system interfaces while maintaining persistence within the restricted environment.