CVE-2001-0061 in FreeBSD
Summary
by MITRE
procfs in FreeBSD and possibly other operating systems does not properly restrict access to per-process mem and ctl files, which allows local users to gain root privileges by forking a child process and executing a privileged process from the child, while the parent retains access to the child s address space.
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Analysis
by VulDB Data Team • 05/29/2018
The vulnerability described in CVE-2001-0061 represents a critical privilege escalation flaw within the procfs filesystem implementation across FreeBSD and potentially other operating systems. This issue stems from inadequate access controls on specific process memory and control files that are exposed through the proc filesystem interface. The fundamental problem lies in how the system handles permissions for these sensitive files, particularly those related to memory mapping and process control operations. When a local user can manipulate these files, they can exploit the underlying design flaw to elevate their privileges from standard user level to root access, creating a severe security risk for affected systems.
The technical exploitation mechanism involves a sophisticated process manipulation technique where an attacker creates a child process that executes a privileged operation while maintaining access to the child's memory space through the parent process. This approach leverages the inherent relationship between parent and child processes within the operating system's memory management architecture. The vulnerability specifically targets the mem and ctl files within procfs, which contain critical information about process memory mappings and control parameters. These files are typically restricted to prevent unauthorized access, but the flaw allows local users to bypass these protections through careful process forking and memory access manipulation.
From an operational perspective, this vulnerability presents a significant threat to system integrity and security posture as it enables local attackers to gain root privileges without requiring any special authentication or network access. The attack vector is particularly dangerous because it operates entirely within the local system environment, making detection more challenging and the attack surface broader. The exploit requires minimal privileges initially, as the attacker only needs standard user access to execute the malicious code. Once successful, the compromised system becomes fully vulnerable to complete control, allowing attackers to modify system files, install backdoors, or extract sensitive information from the entire system.
The vulnerability aligns with several cybersecurity frameworks and threat modeling concepts, including CWE-264, which addresses permissions, privileges, and access controls in operating systems. This weakness specifically manifests as a failure to properly enforce access restrictions on system-critical files within the process filesystem. The attack pattern follows elements of the MITRE ATT&CK framework's privilege escalation tactics, particularly focusing on the "Process Injection" and "Exploitation for Privilege Escalation" techniques. The vulnerability also demonstrates characteristics of the "Local Privilege Escalation" category, where attackers exploit system weaknesses to gain elevated permissions without requiring network-based access or user authentication. Organizations should implement immediate mitigations including system updates, process file permission restrictions, and monitoring for suspicious process creation patterns to protect against exploitation of this vulnerability.
The remediation approach requires comprehensive system updates and patches from the operating system vendors, as the vulnerability exists in the core filesystem implementation. Administrators should also consider implementing additional security controls such as mandatory access controls, process monitoring, and privilege separation mechanisms to reduce the potential impact of similar vulnerabilities. Regular security auditing of process filesystem permissions and memory access controls should be part of routine system maintenance to prevent exploitation of similar weaknesses that may arise in the future.