CVE-2018-8921 in Drive
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in File Sharing Notify Toast in Synology Drive before 1.0.2-10275 allows remote authenticated users to inject arbitrary web script or HTML via the malicious file name.
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Analysis
by VulDB Data Team • 10/17/2024
The vulnerability identified as CVE-2018-8921 represents a critical cross-site scripting flaw within Synology Drive's File Sharing Notify Toast functionality. This issue affects versions prior to 1.0.2-10275 and specifically targets the file sharing notification system that displays toast notifications to users when files are shared or updated. The vulnerability arises from inadequate input validation and sanitization of file names within the notification mechanism, creating an exploitable vector 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 the application's failure to properly sanitize user-supplied file names before rendering them in toast notifications. When a user shares a file containing malicious script tags within its name, the system processes this input without adequate filtering mechanisms. This flaw aligns with CWE-79, which categorizes cross-site scripting vulnerabilities as a result of insufficient input validation and output encoding. The vulnerability operates under the principle that user-controllable data is directly embedded into web pages without proper sanitization, allowing attackers to inject malicious payloads that execute in the victim's browser context.
The operational impact of this vulnerability extends beyond simple script injection, as it enables authenticated attackers to potentially escalate privileges and access sensitive user data. An attacker with valid credentials can manipulate file names to include malicious JavaScript code that executes when other users view the notification. This creates a persistent threat vector where malicious actors can establish backdoors, steal session cookies, or perform actions on behalf of legitimate users. The vulnerability is particularly concerning in enterprise environments where Synology Drive is used for collaborative file sharing, as it can compromise multiple user accounts simultaneously.
The attack surface for this vulnerability is significant given that it requires only authenticated access, making it accessible to any user with valid login credentials. Attackers can leverage this weakness by creating files with malicious names containing script tags such as <script>alert(1)</script> or more sophisticated payloads that establish persistent command and control channels. The vulnerability demonstrates a classic case of insufficient output escaping as outlined in the ATT&CK framework under T1059.007 for Scripting and T1566.001 for Phishing, where attackers exploit notification systems to deliver malicious payloads to unsuspecting users. Organizations using Synology Drive are particularly vulnerable because the notification system is designed to be visible and interactive, making it an ideal vector for delivering malicious content.
Mitigation strategies should focus on immediate patch application to versions 1.0.2-10275 or later, which contain proper input sanitization and output encoding mechanisms. Network administrators should implement additional security controls including web application firewalls that can detect and block suspicious script patterns in file names and notification content. Regular security audits of file sharing systems should be conducted to identify similar input validation gaps, while user education programs should emphasize the dangers of sharing files with unknown or untrusted sources. The implementation of Content Security Policy headers and proper HTML encoding of all user-controllable data in notification systems will provide additional layers of defense against similar vulnerabilities in the future.