CVE-2018-8928 in CardDAV Server
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in Address Book Editor in Synology CardDAV Server before 6.0.8-0086 allows remote authenticated users to inject arbitrary web script or HTML via the (1) family_name, (2) given_name, or (3) additional_name parameter.
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Analysis
by VulDB Data Team • 04/03/2023
The CVE-2018-8928 vulnerability represents a critical cross-site scripting flaw within Synology's CardDAV Server Address Book Editor component. This vulnerability affects versions prior to 6.0.8-0086 and specifically targets the server's handling of user input in three distinct parameters: family_name, given_name, and additional_name. The flaw enables authenticated attackers to inject malicious web scripts or HTML content into the address book entries, creating a persistent XSS vector that can compromise user sessions and data integrity. The vulnerability exists due to insufficient input validation and output encoding mechanisms within the CardDAV server's user interface processing layer.
The technical implementation of this vulnerability stems from the server's failure to properly sanitize user-supplied input before rendering it within web pages. When legitimate users access address book entries containing maliciously crafted input in the targeted parameters, the unfiltered content gets executed in the context of other users' browsers. This creates a classic persistent XSS scenario where the malicious code persists in the server's database and executes whenever affected users view the compromised entries. The vulnerability aligns with CWE-79 which specifically addresses cross-site scripting flaws in web applications, and represents a direct violation of secure input validation principles. Attackers can leverage this weakness to execute arbitrary JavaScript code, potentially stealing session cookies, redirecting users to malicious sites, or performing unauthorized actions on behalf of victims.
The operational impact of CVE-2018-8928 extends beyond simple script injection, as it enables attackers to establish persistent footholds within organizations using Synology NAS devices. Authenticated users with access to the CardDAV server can exploit this vulnerability to compromise other users within the same organization, particularly in environments where address book entries are frequently accessed and shared. The attack surface is amplified by the fact that many organizations rely heavily on CardDAV servers for contact management and synchronization across multiple platforms. This vulnerability can be exploited through various attack vectors including social engineering campaigns targeting administrative users, or through compromised legitimate accounts that have access to the CardDAV functionality. The persistent nature of the vulnerability means that once exploited, malicious payloads remain active until the affected entries are manually removed or the server is patched, creating long-term exposure windows.
Mitigation strategies for CVE-2018-8928 should prioritize immediate patch deployment to update Synology CardDAV Server to version 6.0.8-0086 or later, which contains the necessary input validation and sanitization fixes. Organizations should also implement additional defensive measures including web application firewalls that can detect and block suspicious input patterns, enhanced monitoring of address book modifications, and regular security audits of CardDAV server configurations. Network segmentation and principle of least privilege access controls should be enforced to limit the potential impact of successful exploitation attempts. Security teams should also consider implementing content security policies and regular vulnerability scanning to identify similar weaknesses in other components of their Synology NAS infrastructure. The vulnerability demonstrates the importance of proper input validation and output encoding as outlined in the OWASP Top Ten and aligns with ATT&CK technique T1059.007 for command and scripting interpreter execution, emphasizing the need for comprehensive security controls beyond simple patch management.