CVE-2018-15906 in Serv-U FTP Server
Summary
by MITRE
SolarWinds Serv-U FTP Server 15.1.6 allows remote authenticated users to execute arbitrary code by leveraging the Import feature and modifying a CSV file.
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Analysis
by VulDB Data Team • 08/03/2023
The vulnerability identified as CVE-2018-15906 affects SolarWinds Serv-U FTP Server version 15.1.6 and represents a critical code execution flaw that can be exploited by authenticated remote attackers. This vulnerability resides within the server's import functionality, specifically when processing CSV files through the import feature. The flaw enables malicious actors who have already established authentication credentials to manipulate the import process and subsequently execute arbitrary code on the affected system. The attack vector requires the attacker to possess valid user credentials, making this a privilege escalation vulnerability rather than a purely remote exploit. The security implications are severe as successful exploitation could allow attackers to gain full control over the FTP server, potentially leading to data breaches, lateral movement within networks, or use as a foothold for broader attacks.
The technical root cause of this vulnerability stems from inadequate input validation and sanitization within the CSV import module of the Serv-U FTP server. When users attempt to import user accounts or configuration data through CSV files, the system fails to properly validate or sanitize the imported data before processing it. This lack of proper data validation creates a path for attackers to inject malicious payloads or manipulate the import process to execute unintended commands. The vulnerability is classified as a command injection or code execution flaw that can be leveraged through the import functionality, making it particularly dangerous in environments where administrative or high-privilege accounts exist. The flaw essentially allows an authenticated user to bypass normal access controls and execute arbitrary code with the privileges of the Serv-U service account, which typically runs with elevated system permissions.
The operational impact of CVE-2018-15906 extends beyond simple code execution, as it can facilitate significant compromise of network infrastructure. Attackers who exploit this vulnerability can potentially access sensitive data stored on the FTP server, modify user accounts, or use the compromised system as a pivot point for attacking other network resources. The vulnerability affects organizations that rely on Serv-U FTP servers for file transfer operations, particularly those with multiple user accounts and administrative access. The fact that exploitation requires authentication makes this a particularly concerning flaw because it can be leveraged by malicious insiders or attackers who have obtained valid credentials through various means such as credential theft, social engineering, or weak authentication practices. Organizations using this software may face compliance violations and security breaches if this vulnerability remains unpatched.
Mitigation strategies for CVE-2018-15906 should focus on immediate patching of the affected Serv-U FTP server version, as SolarWinds released updates to address this specific vulnerability. Organizations should also implement additional security controls including network segmentation to limit access to FTP server functionality, implementing strict access controls and monitoring for unusual import activities, and conducting regular security assessments of file transfer systems. The vulnerability aligns with CWE-74, which describes "Improper Neutralization of Special Elements in Output Used by a Downstream Component," and may also relate to CWE-94, "Improper Control of Generation of Code ('Code Injection')." From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and execution through legitimate system tools, specifically T1059.001 for command and scripting interpreter and T1068 for exploit for privilege escalation. Organizations should also consider implementing principle of least privilege for FTP server accounts and regularly auditing import activities to detect potential exploitation attempts.