CVE-2018-8915 in Calendar
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in Notification Center in Synology Calendar before 2.1.1-0502 allows remote authenticated users to inject arbitrary web script or HTML via title parameter.
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Analysis
by VulDB Data Team • 03/11/2023
The vulnerability identified as CVE-2018-8915 represents a critical cross-site scripting flaw within Synology Calendar's Notification Center component affecting versions prior to 2.1.1-0502. This weakness resides in the improper sanitization of user input parameters, specifically the title field used in calendar event notifications. The vulnerability enables authenticated attackers who already possess valid credentials to execute malicious scripts within the context of other users' browsers, creating a significant security risk for organizations relying on Synology's calendar services.
The technical implementation of this vulnerability stems from insufficient input validation and output encoding mechanisms within the calendar application's notification handling system. When users create calendar events or modify existing ones, the title parameter is not adequately sanitized before being rendered in the web interface. This allows attackers to inject malicious HTML content or JavaScript code that executes in the browser of any user who views the affected notification. The flaw operates as a classic reflected XSS attack vector where malicious payloads are embedded in the title field and subsequently executed when the notification is displayed.
From an operational impact perspective, this vulnerability creates substantial risk for enterprise environments where Synology Calendar is extensively used for business communications. An authenticated attacker could exploit this weakness to steal session cookies, perform unauthorized actions on behalf of other users, or redirect victims to malicious websites. The attack requires only legitimate user credentials, making it particularly dangerous as it bypasses many traditional perimeter security controls. Organizations may experience unauthorized access to sensitive calendar data, potential data exfiltration, and compromise of user privacy. The vulnerability affects the core functionality of calendar applications and can be leveraged to escalate privileges within the application context.
The security implications extend beyond immediate exploitation as this vulnerability aligns with CWE-79 which specifically addresses cross-site scripting flaws in software applications. The ATT&CK framework categorizes this as a web application attack vector under the technique of "Cross-Site Scripting" with potential for privilege escalation and credential theft. Organizations should prioritize immediate patching of affected systems, implementing proper input validation measures, and monitoring for suspicious activity in calendar notification systems. The recommended mitigation strategy involves upgrading to Synology Calendar version 2.1.1-0502 or later, which includes proper sanitization of user inputs and enhanced output encoding mechanisms. Additional defensive measures include implementing content security policies, regular security assessments of web applications, and user education regarding the risks of clicking on suspicious calendar notifications. Organizations should also consider network segmentation and access controls to limit the potential impact of such vulnerabilities within their infrastructure.