CVE-2018-16792 in SFTP SCP Server
Summary
by MITRE
SolarWinds SFTP/SCP server through 2018-09-10 is vulnerable to XXE via a world readable and writable configuration file that allows an attacker to exfiltrate data.
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Analysis
by VulDB Data Team • 04/17/2020
The vulnerability identified as CVE-2018-16792 affects SolarWinds SFTP/SCP server versions released through September 10, 2018, presenting a critical security flaw that enables unauthorized data exfiltration through XML External Entity processing. This vulnerability stems from improper handling of XML input within the server's configuration management system, creating an exploitable path for malicious actors to access sensitive system information.
The technical root cause of this vulnerability lies in the server's failure to properly sanitize XML data when processing configuration files that are simultaneously world-readable and world-writable. This configuration file accessibility creates an attack surface where remote adversaries can manipulate the XML parsing mechanism to reference external entities, thereby enabling them to extract arbitrary data from the target system. The vulnerability operates through a classic XXE attack vector where the server processes external entity references without adequate input validation or sanitization.
The operational impact of this vulnerability extends beyond simple data exfiltration, as it provides attackers with the capability to access system resources, configuration details, and potentially sensitive credentials stored within the server environment. The world-readable and writable nature of the configuration file eliminates proper access controls that would normally prevent unauthorized modifications, allowing attackers to craft malicious XML payloads that can be processed by the vulnerable server. This creates a persistent threat vector that can be exploited repeatedly without requiring additional authentication or privileged access.
Security professionals should recognize this vulnerability as a manifestation of CWE-611, which addresses improper restriction of XML external entity reference, and aligns with ATT&CK technique T1074.001 for data staging through external remote services. The vulnerability demonstrates how poor file permission management combined with inadequate XML processing controls can create severe security implications. Organizations should implement immediate mitigations including restricting file permissions on configuration files, implementing proper XML input validation, and applying the vendor-provided security patches released after the vulnerability disclosure. The remediation process should also include comprehensive network monitoring to detect any suspicious XML processing activities that may indicate exploitation attempts.