CVE-2018-8923 in File Station
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in Attachment Preview in Synology File Station before 1.1.4-0122 allows remote authenticated users to inject arbitrary web script or HTML via malicious attachments.
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Analysis
by VulDB Data Team • 03/21/2023
The CVE-2018-8923 vulnerability represents a critical cross-site scripting flaw discovered in Synology File Station's Attachment Preview functionality prior to version 1.1.4-0122. This vulnerability exists within the web-based file management system that is part of Synology's DiskStation Manager ecosystem, which is widely deployed in both enterprise and home networking environments. The flaw specifically affects the way the system processes and displays file attachments, creating an avenue for malicious actors to execute arbitrary web scripts or HTML code within the context of authenticated user sessions.
The technical implementation of this vulnerability stems from insufficient input validation and output encoding within the Attachment Preview component of File Station. When users access certain file types through the web interface, the system fails to properly sanitize user-supplied data that may be embedded within file metadata or content. This inadequate sanitization allows authenticated attackers to upload or manipulate attachments containing malicious scripts that execute in the browser context of other users who view these attachments. The vulnerability is particularly concerning because it requires only authentication to exploit, meaning that any user with valid credentials can leverage this flaw against other users within the same system.
The operational impact of this vulnerability extends beyond simple script execution, as it can enable sophisticated attack vectors including session hijacking, credential theft, and privilege escalation within the targeted environment. Attackers can craft malicious attachments that, when previewed by other users, could redirect them to phishing sites, steal session cookies, or even execute commands on behalf of the victim. This presents a significant risk to organizations relying on Synology File Station for document sharing and collaboration, as the attack surface is broadened by the fact that legitimate users frequently preview various file types including documents, images, and compressed archives. The vulnerability aligns with CWE-79 which specifically addresses Cross-site Scripting flaws, and can be mapped to ATT&CK technique T1059.007 for Scripting, particularly when considering the execution of malicious scripts through browser-based interfaces.
Mitigation strategies for CVE-2018-8923 require immediate patching of affected Synology File Station installations to version 1.1.4-0122 or later, which incorporates proper input validation and output encoding mechanisms. Organizations should also implement network segmentation to limit access to File Station functionality, enforce strict access controls through role-based permissions, and consider deploying web application firewalls to monitor and filter suspicious requests. Additionally, security awareness training for users can help identify potentially malicious attachments, while regular vulnerability assessments should be conducted to ensure that other components within the DiskStation Manager ecosystem remain secure. The remediation process should also include monitoring for any suspicious activity related to file preview operations and implementing automated patch management processes to prevent similar vulnerabilities from being exploited in the future.