CVE-2007-6415 in Linux
Summary
by MITRE
scponly 4.6 and earlier allows remote authenticated users to bypass intended restrictions and execute arbitrary code by invoking scp, as implemented by OpenSSH, with the -F and -o options.
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Analysis
by VulDB Data Team • 08/04/2019
The vulnerability identified as CVE-2007-6415 affects scponly versions 4.6 and earlier, representing a critical security flaw in the restricted shell implementation designed to limit user access to system resources. This vulnerability specifically targets the scp command functionality within OpenSSH's scponly environment, where the security restrictions intended to prevent unauthorized access are bypassed through specific command line argument manipulation. The flaw exists in how the system processes the -F and -o options of the scp command, which are typically used for specifying configuration files and arbitrary options respectively. When these options are properly crafted by authenticated remote users, they can circumvent the intended security boundaries of the restricted shell environment.
The technical mechanism behind this vulnerability involves the improper handling of command line arguments in the scponly implementation, where the -F option allows specifying an alternative configuration file and the -o option enables arbitrary option specification. Attackers can leverage these legitimate features to inject commands that execute outside the intended restricted environment. This represents a classic example of command injection vulnerability where legitimate system interfaces are abused to bypass access controls. The vulnerability is classified under CWE-78 as a failure to sanitize or validate command line arguments, and more specifically aligns with CWE-20 for improper input validation. The flaw demonstrates a failure in the principle of least privilege where authenticated users can escalate their privileges beyond the intended restrictions.
From an operational impact perspective, this vulnerability allows remote authenticated users to execute arbitrary code on the target system with elevated privileges, potentially leading to complete system compromise. The attack requires only authentication credentials and can be performed remotely, making it particularly dangerous in environments where scponly is used to provide restricted access to system resources. The vulnerability affects systems where scponly is configured as a restricted shell for users who need file transfer capabilities but should not have full shell access. This includes scenarios such as ftp users, backup accounts, or any service accounts that require scp functionality but should be restricted from executing arbitrary commands. The exploitation of this vulnerability can result in data exfiltration, system compromise, privilege escalation, and potential lateral movement within the network infrastructure.
The mitigation strategies for CVE-2007-6415 primarily involve upgrading to scponly version 4.7 or later, where the vulnerability has been addressed through proper input validation and argument handling. System administrators should also implement additional security measures including restricting the use of scp command options, monitoring for suspicious command usage patterns, and implementing network-level restrictions to prevent unauthorized access to systems running vulnerable versions. The vulnerability highlights the importance of proper input validation in security-critical applications and aligns with ATT&CK technique T1059.001 for command and scripting interpreter, specifically focusing on how legitimate system tools can be abused for privilege escalation. Organizations should also consider implementing principle of least privilege controls, regularly updating security software, and conducting vulnerability assessments to identify similar issues in other restricted shell implementations. The fix typically involves stricter validation of command line arguments and proper sanitization of user inputs to prevent arbitrary command execution within restricted environments.