CVE-2016-4446 in setroubleshoot
Summary
by MITRE
The allow_execstack plugin for setroubleshoot allows local users to execute arbitrary commands by triggering an execstack SELinux denial with a crafted filename, related to the commands.getoutput function.
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Analysis
by VulDB Data Team • 11/28/2022
The CVE-2016-4446 vulnerability resides within the allow_execstack plugin component of setroubleshoot, a security tool designed to help users understand and resolve SELinux policy violations. This flaw represents a critical privilege escalation vector that enables local attackers to execute arbitrary code on systems running SELinux-enforcing policies. The vulnerability specifically exploits how the plugin handles SELinux denials, creating a dangerous condition where user-controlled input can be manipulated to trigger unintended command execution.
The technical implementation of this vulnerability leverages the commands.getoutput function, which is susceptible to command injection when processing user-provided filenames. When a malicious user crafts a filename containing shell metacharacters or command sequences, the allow_execstack plugin inadvertently passes this input to the getoutput function without proper sanitization. This creates a classic command injection scenario where arbitrary shell commands can be executed with the privileges of the setroubleshoot process, which typically runs with elevated permissions to interact with SELinux policies.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it can be exploited to bypass SELinux protections entirely. Attackers can use this technique to execute arbitrary code with system-level privileges, potentially leading to complete system compromise. The vulnerability is particularly concerning because it operates within the legitimate security monitoring framework, making detection more difficult. The attack requires only local access and knowledge of the specific plugin behavior, making it accessible to any user with basic system privileges.
From a cybersecurity perspective, this vulnerability aligns with CWE-78, which describes improper neutralization of special elements used in OS commands, and maps to ATT&CK technique T1059.001 for command and scripting interpreter. The flaw demonstrates how security tools themselves can become attack vectors when not properly hardened against user input manipulation. Organizations running SELinux systems with setroubleshoot installed face significant risk, as this vulnerability can be exploited without requiring network access or specialized attack infrastructure. The exploitation process is straightforward and reliable, making it a preferred method for attackers seeking to escalate privileges on affected systems.
Mitigation strategies should focus on immediate patching of the setroubleshoot package to address the command injection vulnerability. System administrators should also consider disabling the allow_execstack plugin if it is not essential for their security operations, as this removes the attack surface entirely. Additionally, implementing proper input validation and sanitization within the plugin's handling of filenames can prevent similar issues in other security tools. Regular security audits of security tool configurations and privilege escalation mechanisms should be conducted to identify potential similar vulnerabilities. Organizations should also monitor for anomalous execution patterns in SELinux denials that might indicate exploitation attempts, as the vulnerability operates within legitimate security monitoring processes.