CVE-2000-0992 in SSH
Summary
by MITRE
Directory traversal vulnerability in scp in sshd 1.2.xx allows a remote malicious scp server to overwrite arbitrary files via a .. (dot dot) attack.
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Analysis
by VulDB Data Team • 12/17/2024
The vulnerability described in CVE-2000-0992 represents a critical directory traversal flaw within the secure copy protocol implementation of openssh versions 1.2.x. This security weakness specifically affects the scp command functionality when used in conjunction with sshd servers, creating a scenario where malicious actors can exploit the protocol's file handling mechanisms to gain unauthorized access to the file system. The vulnerability stems from insufficient input validation and path resolution checks within the scp implementation, allowing attackers to manipulate file paths through directory traversal sequences.
The technical exploitation of this vulnerability occurs when a malicious scp server attempts to overwrite arbitrary files on the target system by utilizing the .. (dot dot) traversal sequences in file paths. This attack vector leverages the fundamental flaw in how scp processes relative path references, specifically failing to properly sanitize or validate the paths before executing file operations. When scp receives a file path containing directory traversal elements, it processes these sequences without adequate safeguards, potentially allowing access to files outside the intended directory scope. The vulnerability is particularly dangerous because it can be exploited remotely through a malicious scp server, meaning that an attacker does not need local system access to carry out the attack.
The operational impact of this vulnerability extends beyond simple file overwrites to encompass potential system compromise and data integrity violations. An attacker exploiting this vulnerability could overwrite critical system files, configuration files, or user data, leading to system instability, unauthorized access, or complete system compromise. The vulnerability affects the core security model of scp, which is designed to provide secure file transfer between hosts, making it a significant threat to any system relying on this protocol for file operations. This weakness undermines the trust model that secure protocols like scp are supposed to establish, as it allows for unauthorized file system manipulation through what should be a secure communication channel.
The vulnerability aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal. This classification reflects the fundamental flaw in how the scp implementation handles file paths and validates user input. From an attack framework perspective, this vulnerability would map to multiple ATT&CK techniques including T1078 for valid accounts and T1566 for phishing, as attackers might use compromised accounts to establish malicious scp servers or exploit this weakness to gain unauthorized access to systems. The vulnerability also relates to T1499 which covers endpoint disruption through data manipulation, as the ability to overwrite arbitrary files can lead to system instability and data corruption.
Mitigation strategies for CVE-2000-0992 primarily focus on updating to patched versions of openssh where the directory traversal vulnerability has been addressed through proper input validation and path sanitization. System administrators should immediately upgrade to openssh versions that have resolved this vulnerability, as the issue affects older versions that are no longer supported. Additionally, network segmentation and firewall rules can help limit the exposure of systems running vulnerable versions of sshd, while monitoring for unusual scp activity can help detect potential exploitation attempts. The implementation of proper access controls and the principle of least privilege can also reduce the potential impact of successful exploitation, as attackers would need elevated privileges to overwrite critical system files. Organizations should also implement regular vulnerability assessments and security audits to identify and remediate similar weaknesses in their security infrastructure.