CVE-2016-10118 in Firejail
Summary
by MITRE
Firejail allows local users to truncate /etc/resolv.conf via a chroot command to /.
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Analysis
by VulDB Data Team • 08/30/2020
The vulnerability identified as CVE-2016-10118 resides within the Firejail sandboxing framework, a security tool designed to provide lightweight application sandboxing using Linux namespaces and seccomp-bpf. This particular flaw represents a privilege escalation vulnerability that allows local users to manipulate system configuration files through improper handling of the chroot command. The issue specifically affects the /etc/resolv.conf file which contains DNS resolver configuration information critical for network name resolution across the system. When Firejail executes commands within a chroot environment, it fails to properly validate or restrict file operations that could result in file truncation or modification of system-critical configuration files.
The technical implementation of this vulnerability stems from Firejail's insufficient access control mechanisms when processing chroot operations. The chroot command, when executed with elevated privileges, can potentially truncate or overwrite system files if proper file system permission checks are not enforced. In this specific case, the vulnerability manifests when Firejail processes a chroot command that targets the root directory, allowing malicious local users to exploit the lack of proper file system boundary enforcement. This flaw falls under the category of improper privilege management and inadequate input validation, aligning with CWE-276 which addresses incorrect permissions for critical resources. The vulnerability demonstrates a classic example of insufficient privilege separation where the sandboxing mechanism fails to properly isolate file system operations from system-critical files.
The operational impact of CVE-2016-10118 extends beyond simple file truncation, as the /etc/resolv.conf file serves as a fundamental component of the system's network resolution infrastructure. When this file is truncated or modified by an attacker, it can result in complete disruption of network name resolution services, potentially affecting all applications and services that depend on DNS lookups. This vulnerability can be exploited by local users to gain elevated privileges, as the compromised DNS configuration can be leveraged to redirect network traffic or disable critical system functions. The attack vector requires local system access but does not necessitate network connectivity, making it particularly dangerous in multi-user environments where privilege escalation could lead to full system compromise. This vulnerability directly relates to ATT&CK technique T1068 which covers privilege escalation through local exploitation of system vulnerabilities.
Mitigation strategies for CVE-2016-10118 should focus on immediate patching of Firejail installations to address the specific chroot handling flaw. System administrators should ensure that all Firejail components are updated to versions that properly enforce file system access controls and prevent unauthorized truncation of system configuration files. Additional protective measures include implementing proper file system permissions for /etc/resolv.conf, utilizing file integrity monitoring tools to detect unauthorized modifications, and conducting regular security audits of sandboxing configurations. The vulnerability highlights the importance of proper privilege separation in sandboxing solutions and demonstrates why security tools must implement comprehensive access control mechanisms rather than relying solely on namespace isolation. Organizations should also consider implementing additional monitoring for suspicious chroot operations and file system modifications to detect potential exploitation attempts before they can cause significant damage to system integrity.