CVE-2018-10240 in Serv-U MFT
Summary
by MITRE
SolarWinds Serv-U MFT before 15.1.6 HFv1 assigns authenticated users a low-entropy session token that can be included in requests to the application as a URL parameter in lieu of a session cookie. This session token's value can be brute-forced by an attacker to obtain the corresponding session cookie and hijack the user's session.
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Analysis
by VulDB Data Team • 02/06/2020
The vulnerability identified as CVE-2018-10240 affects SolarWinds Serv-U MFT versions prior to 15.1.6 HFv1, representing a critical session management flaw that undermines the security of authenticated user sessions. This issue stems from the application's implementation of session tokens that contain insufficient entropy, making them susceptible to brute-force attacks. The vulnerability allows attackers to exploit weak session token generation by including the token as a URL parameter rather than relying on traditional session cookies, effectively bypassing standard security mechanisms that typically protect against session hijacking attempts.
The technical flaw manifests in the predictable nature of session tokens generated by the Serv-U MFT application, which operate with low entropy values that significantly reduce the cryptographic strength of the session identifiers. This weakness enables attackers to systematically guess or brute-force session tokens through automated tools and algorithms, ultimately obtaining valid session cookies that correspond to legitimate user sessions. The vulnerability specifically affects the authentication flow where session tokens are transmitted via URL parameters, a practice that exposes these identifiers to interception and exploitation through various attack vectors including network monitoring, log analysis, and direct URL manipulation.
From an operational impact perspective, this vulnerability creates a severe risk for organizations relying on SolarWinds Serv-U MFT for file transfer operations, as successful exploitation allows attackers to gain unauthorized access to user sessions without requiring valid credentials or exploiting other authentication mechanisms. The session hijacking capability enables attackers to perform actions with the privileges of authenticated users, potentially leading to data exfiltration, unauthorized file transfers, system compromise, and persistence within the network environment. The vulnerability affects all authenticated users within the application, making it particularly dangerous as it can be exploited against any legitimate session without requiring specific user targeting or advanced attack techniques.
The security implications of this vulnerability align with CWE-330, which addresses insufficient entropy in random number generation, and can be mapped to ATT&CK technique T1563.002 for credential access through session hijacking. Organizations should implement immediate mitigations including updating to SolarWinds Serv-U MFT version 15.1.6 HFv1 or later, which addresses the weak session token generation, and implementing additional security controls such as enforcing secure session cookie attributes, implementing rate limiting on authentication attempts, and monitoring for suspicious session token usage patterns. Network segmentation and logging improvements should also be considered to detect and prevent exploitation attempts, while administrators should review and rotate existing session tokens to mitigate potential ongoing threats.