CVE-2005-4533 in scponly
Summary
by MITRE
Argument injection vulnerability in scponlyc in scponly 4.1 and earlier, when both scp and rsync compatability are enabled, allows local users to execute arbitrary applications via "getopt" style argument specifications, which are not filtered.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 07/27/2019
The CVE-2005-4533 vulnerability represents a critical argument injection flaw within the scponlyc component of the scponly 4.1 software suite, specifically affecting systems where both scp and rsync compatibility modes are enabled. This vulnerability resides in the way the system processes command-line arguments during file transfer operations, creating a pathway for malicious input to be interpreted as executable commands rather than simple parameters. The flaw fundamentally stems from inadequate input sanitization mechanisms that fail to properly filter or validate argument specifications, particularly those following getopt style conventions commonly used in Unix-like systems for parsing command-line options.
The technical implementation of this vulnerability exploits the trust placed in argument parsing within the scponlyc binary, which operates as a restricted shell for secure file transfers. When both scp and rsync compatibility modes are active, the system processes user-provided arguments without sufficient validation, allowing local attackers to inject malicious command-line parameters that bypass normal security boundaries. The getopt style argument specifications, which typically begin with dashes and may include options such as -l, -r, -v, or other standard Unix command-line flags, become vectors for arbitrary code execution when not properly filtered. This creates a scenario where an attacker can craft input that appears to be legitimate command-line arguments but actually contains executable commands that the system processes with elevated privileges.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it allows local users to execute arbitrary applications with the privileges of the scponlyc process. This can result in complete system compromise, data exfiltration, or the establishment of persistent backdoors within the affected environment. The vulnerability is particularly dangerous because it operates within a restricted shell context, meaning that attackers can leverage this flaw to bypass security controls designed to limit user capabilities while performing file transfer operations. The exploitability of this vulnerability is enhanced by the fact that it requires minimal privileges to trigger, making it accessible to any local user who can interact with the scponlyc binary.
Mitigation strategies for CVE-2005-4533 must address the fundamental flaw in argument validation and input filtering within the scponlyc implementation. Organizations should immediately upgrade to scponly versions 4.2 or later, where the argument injection vulnerability has been resolved through enhanced input sanitization and proper argument validation mechanisms. System administrators should disable rsync compatibility mode when it is not required, as this reduces the attack surface by eliminating one of the conditions necessary to exploit the vulnerability. Additionally, implementing proper input validation and sanitization measures, such as those aligned with CWE-77 and CWE-78 standards for command injection prevention, can help protect against similar vulnerabilities in other applications. The ATT&CK framework categorizes this type of vulnerability under privilege escalation techniques, specifically targeting the use of compromised binaries to execute arbitrary code, making it a critical concern for organizations implementing secure file transfer protocols.