CVE-2001-1180 in FreeBSD
Summary
by MITRE
FreeBSD 4.3 does not properly clear shared signal handlers when executing a process, which allows local users to gain privileges by calling rfork with a shared signal handler, having the child process execute a setuid program, and sending a signal to the child.
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Analysis
by VulDB Data Team • 12/15/2024
The vulnerability described in CVE-2001-1180 represents a critical privilege escalation flaw within the FreeBSD operating system version 4.3. This issue stems from improper handling of signal handlers during process execution, specifically when utilizing the rfork system call with shared signal handlers. The vulnerability exists at the kernel level and exploits fundamental process management mechanisms that govern how signal handling is inherited and managed across parent and child processes. The flaw demonstrates a significant oversight in the operating system's security model, where the kernel fails to properly isolate signal handler contexts between processes, creating an exploitable condition that can be leveraged by local attackers to elevate their privileges.
The technical implementation of this vulnerability relies on the rfork system call which allows processes to create new processes with shared memory spaces and signal handlers. When a parent process calls rfork with shared signal handlers, the child process inherits these handlers but fails to properly clear or reset them during execution. This inheritance mechanism becomes problematic when the child process subsequently executes a setuid program, as the inherited signal handlers can be manipulated to gain elevated privileges. The vulnerability specifically exploits the timing and context of signal delivery between parent and child processes, where a signal sent to the child process can trigger code execution within the context of the setuid program, effectively bypassing normal privilege restrictions. This mechanism aligns with CWE-254 vulnerability classification related to security features that are improperly implemented or configured, and represents a classic example of improper privilege management in Unix-like systems.
The operational impact of this vulnerability is severe for any system running FreeBSD 4.3, as it provides local attackers with a straightforward path to privilege escalation without requiring any network access or complex exploitation techniques. The attack vector is relatively simple to execute, requiring only local access to the system and knowledge of the rfork system call behavior. Once successfully exploited, the vulnerability allows attackers to execute code with the privileges of the setuid program, potentially leading to full system compromise. This type of vulnerability is particularly dangerous in multi-user environments where local users might attempt to exploit such conditions to gain unauthorized access to sensitive system resources or escalate their privileges to root level access. The vulnerability demonstrates a fundamental flaw in process isolation mechanisms that should normally prevent such cross-process privilege leakage, making it a critical concern for system administrators and security professionals managing FreeBSD systems.
Mitigation strategies for CVE-2001-1180 primarily involve immediate system updates to newer FreeBSD versions where this vulnerability has been addressed through proper signal handler management and process isolation improvements. System administrators should implement the latest security patches and updates from FreeBSD, as the vulnerability was resolved in subsequent releases through kernel-level fixes that properly clear shared signal handlers during process execution. Additionally, organizations should consider implementing process monitoring and privilege auditing to detect anomalous behavior that might indicate exploitation attempts. The vulnerability highlights the importance of proper signal handler cleanup in kernel code and emphasizes the need for comprehensive security testing of system calls that handle process inheritance. From an ATT&CK framework perspective, this vulnerability maps to privilege escalation techniques using process manipulation and signal handling, demonstrating how low-level kernel flaws can be exploited to achieve high-impact security breaches. System hardening measures including restricting local access, implementing proper user privilege separation, and monitoring for unauthorized process execution should be considered as additional defensive measures against similar vulnerabilities in the broader security landscape.