CVE-2016-10123 in Firejail
Summary
by MITRE
Firejail allows --chroot when seccomp is not supported, which might allow local users to gain privileges.
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Analysis
by VulDB Data Team • 08/30/2020
The vulnerability identified as CVE-2016-10123 affects Firejail, a Linux sandboxing tool designed to restrict application access through Linux namespaces and seccomp-bpf filters. This security flaw exists in the privilege escalation mechanism when Firejail attempts to execute the --chroot command while seccomp filtering is not available on the system. The vulnerability stems from Firejail's inability to properly validate system capabilities before attempting to establish restricted execution environments, creating a potential path for local attackers to bypass intended security controls.
Firejail operates by creating isolated execution environments for applications using various Linux kernel features including user namespaces, network namespaces, and seccomp-bpf filtering. When seccomp is not supported or disabled on a target system, Firejail's implementation fails to properly handle the absence of this security mechanism during chroot operations. The technical flaw manifests when the sandboxing tool attempts to create a chroot environment without adequate privilege restrictions, potentially allowing malicious processes to escape the sandbox boundaries and elevate their privileges to that of the root user or other elevated accounts.
The operational impact of this vulnerability extends beyond simple privilege escalation as it represents a fundamental flaw in Firejail's security model implementation. Local users who can execute Firejail with elevated privileges or those who have access to systems running vulnerable versions can exploit this weakness to gain unauthorized access to system resources. The vulnerability is particularly concerning because it undermines the core security principle that sandboxed applications should remain isolated from the host system, potentially allowing attackers to access sensitive data, modify system files, or establish persistent backdoors.
This vulnerability aligns with CWE-284, which addresses improper access control in software systems, and demonstrates how inadequate privilege validation can lead to unauthorized system access. From an ATT&CK framework perspective, this represents a privilege escalation technique that leverages the weakness in sandboxing implementation, potentially mapping to T1068 - Exploitation for Privilege Escalation. The flaw essentially allows attackers to bypass the intended security boundaries that should protect against local privilege escalation attacks, making it particularly dangerous in environments where Firejail is used as a security control for application isolation.
Mitigation strategies for CVE-2016-10123 should focus on ensuring that Firejail is updated to versions that properly handle systems lacking seccomp support. System administrators should implement comprehensive security monitoring to detect unauthorized Firejail usage patterns and ensure that only trusted users have the ability to execute sandboxed applications. Additionally, organizations should consider implementing alternative security controls such as mandatory access controls, enhanced user privilege management, and regular system auditing to detect potential exploitation attempts. The most effective long-term solution involves updating Firejail to versions that properly validate system capabilities before attempting to establish sandboxed execution environments, ensuring that chroot operations are only performed when appropriate security mechanisms are available.