CVE-2016-1883 in FreeBSD
Summary
by MITRE
The issetugid system call in the Linux compatibility layer in FreeBSD 9.3, 10.1, and 10.2 allows local users to gain privilege via unspecified vectors.
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Analysis
by VulDB Data Team • 07/11/2018
The CVE-2016-1883 vulnerability resides within the Linux compatibility layer of FreeBSD operating systems, specifically affecting versions 9.3, 10.1, and 10.2. This flaw manifests in the issetugid system call which is designed to determine whether a process is running with elevated privileges or if it has been modified by setuid or setgid operations. The vulnerability represents a critical security weakness that enables local attackers to escalate their privileges within the system, potentially compromising the entire operating environment.
The technical implementation of this vulnerability stems from improper handling of privilege checks within the Linux compatibility layer's issetugid system call. When processes execute within the FreeBSD environment that emulates Linux behavior, the system call fails to properly validate the privilege state of calling processes. This oversight creates a condition where malicious local users can manipulate the system's privilege assessment mechanisms and bypass security controls that should prevent unauthorized privilege escalation. The unspecified vectors mentioned in the description indicate that multiple attack paths exist, likely involving various combinations of process manipulation and system call invocation that exploit the flawed privilege validation logic.
From an operational impact perspective, this vulnerability poses significant risks to FreeBSD systems running affected versions, particularly in environments where multiple users share system resources or where privileged services operate within the Linux compatibility layer. Local privilege escalation attacks leveraging CVE-2016-1883 can enable attackers to gain root access or elevated privileges, potentially leading to complete system compromise, data exfiltration, or persistent backdoor installation. The attack surface expands when considering that many enterprise environments utilize FreeBSD for hosting various services that may interact with Linux applications through the compatibility layer, making this vulnerability particularly dangerous in production environments.
Security practitioners should implement immediate mitigations including applying the latest FreeBSD security patches that address the privilege escalation flaw in the Linux compatibility layer. System administrators should also consider disabling the Linux compatibility layer entirely if it is not required for critical operations, as this eliminates the attack surface associated with the vulnerable issetugid system call. Additionally, monitoring for suspicious privilege escalation attempts and implementing proper access controls can help detect potential exploitation attempts. This vulnerability aligns with CWE-284 (Improper Access Control) and may map to ATT&CK techniques involving privilege escalation and persistence mechanisms, particularly those targeting system call interfaces within compatibility layers. The remediation approach should include comprehensive system hardening measures and regular security assessments to ensure that similar privilege escalation vulnerabilities are not present in other system components or compatibility layers.