CVE-2000-0749 in FreeBSD
Summary
by MITRE
Buffer overflow in the Linux binary compatibility module in FreeBSD 3.x through 5.x allows local users to gain root privileges via long filenames in the linux shadow file system.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 08/26/2019
The vulnerability described in CVE-2000-0749 represents a critical buffer overflow flaw within FreeBSD's Linux binary compatibility layer, specifically affecting versions 3.x through 5.x of the operating system. This issue resides in the linux shadow file system implementation where the system fails to properly validate the length of filenames before processing them, creating an exploitable condition that can be leveraged by local attackers to escalate privileges to root level access. The buffer overflow occurs when the system attempts to handle excessively long filenames within the compatibility layer, causing memory corruption that can be manipulated to execute arbitrary code with elevated privileges.
The technical nature of this vulnerability stems from inadequate input validation within the Linux binary compatibility module, which operates as a subsystem allowing FreeBSD to execute linux binaries. When a local user provides a filename that exceeds the allocated buffer size, the system's memory management fails to enforce proper bounds checking, resulting in a classic buffer overflow condition. This flaw specifically impacts the linux shadow file system component that handles user authentication data, making it particularly dangerous as it directly relates to privilege management functions. The vulnerability is classified as a buffer overflow under CWE-121, which represents a common weakness in software design where insufficient bounds checking allows memory corruption.
The operational impact of this vulnerability is severe as it enables local privilege escalation without requiring any special authentication or network access. An attacker with basic user-level access can exploit this condition to gain root privileges, effectively compromising the entire system. The attack vector is particularly concerning because it requires no network connectivity and can be executed locally, making it difficult to detect through traditional network monitoring systems. Once successfully exploited, the attacker gains complete control over the system, including the ability to modify system files, install malware, or establish persistent backdoors. This vulnerability directly aligns with ATT&CK technique T1068, which covers local privilege escalation through exploitation of system vulnerabilities, and T1548.001, which covers abuse of root or administrator privileges.
Mitigation strategies for this vulnerability involve immediate system updates and patches provided by FreeBSD to address the buffer overflow in the linux binary compatibility module. Organizations should ensure that all FreeBSD systems are upgraded to versions that contain the necessary security fixes, as this vulnerability was addressed in subsequent releases. Additionally, administrators should disable the linux binary compatibility layer if it is not essential for system operations, as this would eliminate the attack surface entirely. System monitoring should include detection of unusual filename patterns and process behavior that might indicate exploitation attempts. The implementation of proper input validation and bounds checking within the system's compatibility layer serves as a preventive measure against similar vulnerabilities. Security audits should verify that all binary compatibility modules are properly configured and that unnecessary compatibility features are disabled to reduce the risk of exploitation.