CVE-2018-10241 in Serv-U
Summary
by MITRE
A denial of service vulnerability in SolarWinds Serv-U before 15.1.6 HFv1 allows an authenticated user to crash the application (with a NULL pointer dereference) via a specially crafted URL beginning with the /Web%20Client/ substring.
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Analysis
by VulDB Data Team • 02/06/2020
The vulnerability identified as CVE-2018-10241 represents a critical denial of service flaw within the SolarWinds Serv-U FTP server software. This vulnerability affects versions prior to 15.1.6 HFv1 and demonstrates a classic null pointer dereference condition that can be exploited by authenticated users to crash the application entirely. The flaw specifically manifests when processing specially crafted URLs that begin with the /Web%20Client/ substring, indicating a targeted vulnerability within the web client interface component of the Serv-U server. Such vulnerabilities fall under CWE-476 which defines null pointer dereference as a condition where a null value is dereferenced, leading to application crashes and potential system instability. The impact extends beyond simple service disruption as this vulnerability can be leveraged to create persistent availability issues that affect legitimate users and system operations.
The technical exploitation of this vulnerability requires an authenticated user account, which reduces the attack surface but does not eliminate the risk entirely. Attackers can craft malicious URLs that, when processed by the vulnerable Serv-U server, trigger a null pointer dereference that results in an application crash. This type of vulnerability is particularly concerning because it allows for remote code execution capabilities when combined with other exploitation techniques, though the current description indicates a denial of service rather than arbitrary code execution. The specific URL pattern /Web%20Client/ suggests that the vulnerability exists within the web interface handling logic, where the application fails to properly validate input parameters before attempting to dereference pointers. The exploitation process likely involves sending a crafted HTTP request that contains the specific URL structure, causing the application to attempt to access a null pointer in memory.
From an operational perspective, this vulnerability presents significant risks to organizations that rely on SolarWinds Serv-U for file transfer operations and network services. The ability to crash the application through a simple URL manipulation means that even low-privilege authenticated users can cause service disruptions that may last until manual intervention occurs. This vulnerability is particularly dangerous in environments where continuous availability is critical, such as financial services, healthcare organizations, or any infrastructure where file transfer reliability is paramount. The impact extends to business continuity as service interruptions can affect legitimate file transfers, user access, and overall network operations. The vulnerability's classification under the ATT&CK framework would likely fall under T1499 which covers network denial of service attacks, and potentially T1071 which covers application layer protocol usage. Organizations may also face compliance and regulatory issues if service disruptions occur due to this vulnerability, particularly in industries with strict uptime requirements.
Mitigation strategies for CVE-2018-10241 should prioritize immediate patching of affected systems to version 15.1.6 HFv1 or later, which contains the necessary code fixes to prevent the null pointer dereference condition. Network segmentation and access controls should be implemented to limit the number of authenticated users who can reach the vulnerable web client interface, reducing the potential attack surface. Additionally, implementing robust monitoring and alerting systems can help detect unusual patterns of URL access that may indicate exploitation attempts. Organizations should also consider implementing web application firewalls that can filter out malicious URL patterns before they reach the vulnerable application. The vulnerability's existence highlights the importance of regular security updates and patch management processes, as well as the need for comprehensive security testing of web interfaces. System administrators should also conduct regular vulnerability assessments to identify similar issues within other network services and applications, particularly focusing on input validation and memory management practices that could lead to similar null pointer dereference conditions.