CVE-2000-0614 in Linux
Summary
by MITRE
Tnef program in Linux systems allows remote attackers to overwrite arbitrary files via TNEF encoded compressed attachments which specify absolute path names for the decompressed output.
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Analysis
by VulDB Data Team • 05/27/2018
The vulnerability identified as CVE-2000-0614 resides within the Tnef program functionality found on Linux systems, representing a critical file system security flaw that enables remote attackers to execute unauthorized file overwrites. This vulnerability specifically targets the handling of TNEF encoded compressed attachments, which are commonly used in Microsoft Exchange environments for encapsulating rich text formatting and embedded objects. The Tnef program serves as a utility for extracting content from these proprietary TNEF (Transport Neutral Encapsulation Format) files, which are typically generated when emails contain rich text formatting or embedded objects. When processing TNEF attachments, the program fails to properly validate or sanitize the absolute path names specified within the compressed data, creating a path traversal condition that allows malicious actors to manipulate the output destination of decompressed files. This flaw operates at the core of file system access controls and demonstrates a fundamental failure in input validation and access control mechanisms.
The technical exploitation of this vulnerability occurs when an attacker crafts a malicious TNEF attachment containing compressed data with absolute path specifications that point to system-critical files outside the intended directory structure. The Tnef program, upon decompressing the attachment, blindly follows these absolute paths without proper validation, resulting in the overwriting of arbitrary files on the target system. This behavior directly violates the principle of least privilege and demonstrates a classic path traversal vulnerability pattern that has been documented in numerous security frameworks including CWE-22, which specifically addresses path traversal issues. The flaw essentially allows attackers to bypass normal file system access controls by leveraging the decompression process to write files to locations that should normally be protected or restricted. This vulnerability is particularly dangerous because it can potentially overwrite system binaries, configuration files, or other critical components, thereby enabling privilege escalation or system compromise.
The operational impact of CVE-2000-0614 extends beyond simple file overwrites and represents a significant threat to system integrity and availability. Attackers can exploit this vulnerability to overwrite critical system files, potentially leading to complete system compromise or denial of service conditions. The vulnerability affects any Linux system running the Tnef program that processes untrusted TNEF attachments, making it particularly dangerous in email server environments or systems that handle numerous external email communications. When combined with other attack vectors, this vulnerability can enable attackers to establish persistent access or escalate privileges within the system. The impact is further amplified because the vulnerability does not require authentication to exploit, making it particularly dangerous in environments where email systems are accessible to unauthenticated users. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and persistence mechanisms, as attackers can leverage the ability to overwrite system files to maintain access or elevate their privileges within the compromised environment.
Mitigation strategies for CVE-2000-0614 must address both the immediate vulnerability and broader system security posture. The most effective immediate solution involves patching or updating the Tnef program to implement proper input validation and path sanitization, ensuring that absolute paths are either rejected or properly validated before file operations are performed. System administrators should also implement strict access controls and file system permissions to minimize the impact of potential exploitation attempts. Additionally, organizations should consider implementing email filtering mechanisms that can detect and block suspicious TNEF attachments or sanitize the content before processing. The vulnerability highlights the importance of secure coding practices and input validation, particularly in programs that handle untrusted data from external sources. Security monitoring should include detection of unusual file system access patterns or attempts to write to system-critical directories. Organizations should also consider implementing network segmentation and access controls to limit the potential impact of successful exploitation attempts, while maintaining proper log auditing to detect any unauthorized file modifications that might result from this vulnerability.