CVE-2016-9465 in ownCloud Server
Summary
by MITRE
Nextcloud Server before 10.0.1 & ownCloud Server before 9.0.6 and 9.1.2 suffer from Stored XSS in CardDAV image export. The CardDAV image export functionality as implemented in Nextcloud/ownCloud allows the download of images stored within a vCard. Due to not performing any kind of verification on the image content this is prone to a stored Cross-Site Scripting attack.
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Analysis
by VulDB Data Team • 11/22/2022
The vulnerability described in CVE-2016-9465 represents a critical stored cross-site scripting flaw within the CardDAV image export functionality of Nextcloud and ownCloud server implementations. This security weakness affects versions prior to 10.0.1 for Nextcloud and 9.0.6 and 9.1.2 for ownCloud, creating a persistent threat vector that can compromise user sessions and execute malicious code within the context of affected applications. The vulnerability specifically targets the image export feature that processes vCard data containing embedded images, making it particularly dangerous as it allows attackers to store malicious payloads that persist across multiple user interactions.
The technical implementation flaw stems from inadequate input validation and sanitization within the CardDAV image export module. When users attempt to download images stored within vCard files, the system fails to perform proper content verification or sanitization of image metadata and embedded code. This absence of security controls creates an environment where malicious actors can craft specially formatted vCard files containing malicious JavaScript code within image data. The vulnerability is classified as stored XSS because the malicious code is not executed immediately upon upload but rather when the victim accesses the vulnerable functionality, allowing attackers to establish persistent attack vectors that can affect multiple users over time.
The operational impact of this vulnerability extends beyond simple script execution, as it provides attackers with the ability to hijack user sessions, steal sensitive information, and potentially escalate privileges within the affected systems. When users access the CardDAV image export functionality, the malicious code embedded within the vCard images executes in the victim's browser context, potentially allowing attackers to access stored credentials, modify user data, or redirect users to malicious websites. This vulnerability directly violates security principles outlined in the OWASP Top Ten, specifically addressing the stored XSS category that represents one of the most dangerous forms of cross-site scripting attacks.
The attack surface for this vulnerability is particularly concerning given the widespread adoption of Nextcloud and ownCloud solutions in enterprise and personal environments where contact management and synchronization are critical functions. The implementation of this vulnerability aligns with ATT&CK technique T1566.002 for credential access and T1203 for exploitation for client execution, as attackers can leverage this weakness to gain unauthorized access to user accounts and execute arbitrary code. Organizations using these platforms face significant risk of data breaches, session hijacking, and potential lateral movement within their networks, especially when the affected systems are integrated with other enterprise applications that trust the authenticated user context.
Mitigation strategies for CVE-2016-9465 should prioritize immediate patching of affected versions to the recommended secure releases, while implementing additional defensive measures such as network segmentation, monitoring for unusual vCard file uploads, and regular security assessments of contact management functionalities. Organizations should also consider implementing web application firewalls that can detect and block malicious vCard content, along with user education regarding the risks of downloading unknown contact files. The vulnerability demonstrates the critical importance of input validation and content sanitization in web applications, particularly in features that handle user-provided data, and serves as a reminder of the security implications of not properly validating file content in web-based contact management systems.