CVE-2016-10119 in Firejail
Summary
by MITRE
Firejail uses 0777 permissions when mounting /tmp, which allows local users to gain privileges.
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Analysis
by VulDB Data Team • 08/30/2020
The vulnerability identified as CVE-2016-10119 affects Firejail, a security sandboxing tool designed to provide lightweight containment for applications and processes. This flaw resides in how Firejail handles temporary file system mounting operations, specifically when creating or mounting the /tmp directory within sandboxed environments. The issue stems from Firejail's implementation of overly permissive file system permissions that inadvertently create security risks for local users operating within the system. The core technical problem manifests when Firejail mounts the /tmp filesystem with 0777 permissions, a configuration that grants read, write, and execute access to all users and groups on the system. This permission scheme fundamentally undermines the security model that Firejail aims to establish, as it creates an attack surface that malicious local users can exploit to escalate privileges or manipulate sandboxed processes.
The operational impact of this vulnerability extends beyond simple privilege escalation opportunities, as it directly compromises the integrity and confidentiality of applications running within Firejail sandboxes. When /tmp is mounted with 0777 permissions, local attackers can create symbolic links, overwrite critical files, or inject malicious code into the sandboxed environment. This weakness particularly affects scenarios where Firejail is used to isolate applications that handle sensitive data or process privileged operations. The vulnerability aligns with CWE-732, which describes improper permission assignment, and represents a significant deviation from the principle of least privilege that security tools should enforce. Attackers can leverage this flaw to gain unauthorized access to information or services that should remain protected within the sandboxed environment, effectively neutralizing the security benefits that Firejail is designed to provide.
From a threat modeling perspective, this vulnerability enables local privilege escalation attacks that can be executed with minimal prerequisites, making it particularly dangerous in multi-user environments or systems where Firejail is deployed for security isolation. The flaw creates a persistent security weakness that persists across system reboots and application restarts, as the improper permission settings are applied during the mounting process. Security professionals should note that this vulnerability operates at the file system level and can be exploited through various attack vectors including direct manipulation of temporary files, creation of malicious symbolic links, or exploitation of race conditions within the sandboxed application. The ATT&CK framework categorizes this type of vulnerability under privilege escalation techniques, specifically targeting the T1068 - Exploitation for Privilege Escalation sub-technique where local attackers leverage system weaknesses to gain elevated privileges.
Mitigation strategies for CVE-2016-10119 require immediate attention and should include updating Firejail to versions that properly implement restrictive permissions for temporary file systems. System administrators should verify that /tmp mounting operations use appropriate permission schemes that limit access to the specific user or group context required for the sandboxed application to function. The recommended approach involves implementing stricter permission settings such as 1777 (sticky bit) for /tmp directories or more restrictive access controls that align with the principle of least privilege. Additionally, security monitoring should be enhanced to detect unusual file system access patterns or unauthorized modifications to temporary directories within sandboxed environments. Organizations should also consider implementing additional security controls such as mandatory access controls, file integrity monitoring, and regular security audits to identify and remediate similar permission-related vulnerabilities. The vulnerability serves as a reminder of the critical importance of proper permission management in security tool implementations and underscores the necessity of thorough security testing for sandboxing and containment solutions.