CVE-2007-6350 in scponly
Summary
by MITRE
scponly 4.6 and earlier allows remote authenticated users to bypass intended restrictions and execute code by invoking dangerous subcommands including (1) unison, (2) rsync, (3) svn, and (4) svnserve, as originally demonstrated by creating a Subversion (SVN) repository with malicious hooks, then using svn to trigger execution of those hooks.
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Analysis
by VulDB Data Team • 07/30/2021
The vulnerability described in CVE-2007-6350 affects scponly version 4.6 and earlier, representing a critical security flaw in Unix-like systems where users are restricted to scp operations only. This tool is designed to provide limited shell access for file transfer purposes while preventing execution of arbitrary commands. The vulnerability stems from the improper handling of certain subcommands that are permitted in the restricted environment, specifically unison, rsync, svn, and svnserve. These applications, while legitimate for their intended purposes, can be exploited to bypass the intended security restrictions of scponly.
The technical flaw lies in the execution model of scponly where it does not properly sanitize or restrict the execution of these specific subcommands. When authenticated users invoke these tools through the scponly environment, they can leverage the capabilities of these applications to execute arbitrary code on the target system. The original demonstration of this vulnerability involved creating a malicious Subversion repository with specially crafted hooks that would execute when the svn command was invoked. This represents a classic privilege escalation vector where a user with limited access can leverage the functionality of legitimate system tools to gain unauthorized code execution privileges.
The operational impact of this vulnerability is significant as it allows remote authenticated attackers to completely circumvent the intended security model of scponly. The affected system becomes vulnerable to code execution attacks that can potentially lead to full system compromise, data exfiltration, or further lateral movement within the network. Attackers can exploit this vulnerability to establish persistent access, escalate privileges, or deploy additional malicious payloads. The vulnerability is particularly dangerous because it operates within the context of legitimate user sessions, making detection more challenging and potentially allowing attackers to remain undetected for extended periods.
Mitigation strategies for CVE-2007-6350 involve immediate patching of scponly to version 4.7 or later, which addresses the specific command execution flaws. System administrators should also implement comprehensive monitoring of scponly usage patterns to detect anomalous behavior that might indicate exploitation attempts. The principle of least privilege should be enforced by restricting access to these vulnerable subcommands entirely, particularly when they are not required for legitimate operational purposes. Organizations should consider implementing additional security controls such as mandatory access controls, network segmentation, and regular security audits to prevent exploitation of similar vulnerabilities. This vulnerability aligns with CWE-22, which addresses improper limitation of a pathname to a restricted directory, and maps to ATT&CK technique T1059.001 for command and scripting interpreter, highlighting the need for comprehensive system hardening and access control measures.