CVE-2016-9016 in Firejail
Summary
by MITRE
Firejail 0.9.38.4 allows local users to execute arbitrary commands outside of the sandbox via a crafted TIOCSTI ioctl call.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 05/14/2026
The vulnerability identified as CVE-2016-9016 affects Firejail version 0.9.38.4, a security sandboxing tool designed to isolate applications and prevent them from accessing system resources. This local privilege escalation flaw arises from improper handling of the TIOCSTI ioctl system call, which allows users to inject keystrokes into terminal sessions. The vulnerability represents a critical security weakness that undermines the fundamental purpose of sandboxing by enabling unauthorized command execution beyond the intended isolation boundaries.
The technical flaw stems from Firejail's insufficient validation of ioctl commands passed through the TIOCSTI interface, which is typically used for terminal input simulation. When a malicious local user crafts a specially formatted ioctl call, the sandboxing mechanism fails to properly restrict or sanitize this input, allowing the attacker to execute arbitrary commands with elevated privileges. This occurs because the system does not adequately verify the origin or legitimacy of the ioctl request, creating a pathway for privilege escalation that bypasses the sandbox's protective measures. The vulnerability specifically affects the ioctl subsystem within Firejail's security model, where input validation is insufficient to prevent malicious command injection.
The operational impact of this vulnerability is severe for systems relying on Firejail for application isolation. Local attackers with basic user privileges can exploit this weakness to execute commands as root or with elevated permissions, effectively compromising the entire system. This represents a complete breakdown of the sandboxing security model, as the isolation boundary is breached. The vulnerability allows for arbitrary code execution outside the intended sandbox environment, potentially leading to full system compromise, data exfiltration, and persistent access. Organizations using Firejail for containerization, application isolation, or security hardening may experience significant security breaches when this vulnerability is exploited.
Mitigation strategies for CVE-2016-9016 involve immediate patching of Firejail to version 0.9.38.5 or later, which includes proper ioctl validation and input sanitization. System administrators should also implement additional security controls such as restricting user privileges, monitoring for suspicious ioctl activity, and employing principle of least privilege configurations. The vulnerability aligns with CWE-170, which addresses improper handling of input that can lead to command injection, and maps to ATT&CK technique T1068, which covers local privilege escalation through system weaknesses. Organizations should conduct thorough security assessments of their sandboxing implementations and consider alternative security solutions if Firejail cannot be immediately updated. Regular security audits and vulnerability scanning should be implemented to identify similar weaknesses in other sandboxing tools and system components.