CVE-2022-39331 in Nexcloud
Summary
by MITRE • 11/25/2022
Nexcloud desktop is the Desktop sync client for Nextcloud. An attacker can inject arbitrary HyperText Markup Language into the Desktop Client application in the notifications. It is recommended that the Nextcloud Desktop client is upgraded to 3.6.1. There are no known workarounds for this issue.
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Analysis
by VulDB Data Team • 11/05/2025
The vulnerability identified as CVE-2022-39331 affects the Nextcloud Desktop Client, a widely used desktop synchronization application that enables users to maintain local copies of their Nextcloud data. This client serves as a critical interface between users and cloud storage services, making it an attractive target for attackers seeking to compromise user systems through malicious notifications. The vulnerability specifically resides in how the application processes and displays notification content, creating an opportunity for cross-site scripting attacks that could potentially escalate to more severe security incidents.
The technical flaw manifests as a lack of proper input sanitization within the notification handling mechanism of the Nextcloud Desktop Client. When the application receives notification data from the Nextcloud server, it fails to adequately validate or escape HTML content before rendering it within the client interface. This represents a classic cross-site scripting vulnerability where attacker-controlled data can be injected into the client's display layer. The vulnerability is classified under CWE-79 as a Cross-Site Scripting issue, specifically involving the improper sanitization of user-provided data within client-side applications. The flaw exists in the client-side processing rather than server-side code, making it particularly concerning as it can be exploited through server-side manipulation of notification content.
The operational impact of this vulnerability extends beyond simple notification manipulation, as it creates a potential attack vector for more sophisticated compromises. An attacker who can influence notification content could execute malicious scripts within the context of the desktop client, potentially leading to privilege escalation, data exfiltration, or system compromise. The vulnerability affects all versions prior to 3.6.1, leaving users of older releases exposed to potential exploitation. According to ATT&CK framework, this vulnerability maps to T1059.007 for Scripting and T1566.001 for Phishing, as it enables attackers to deliver malicious payloads through notification-based social engineering attacks. The lack of known workarounds means that users must upgrade to the patched version to achieve protection, as no alternative mitigation strategies are available.
Organizations and individual users should prioritize upgrading to Nextcloud Desktop Client version 3.6.1 or later to remediate this vulnerability. The upgrade process should be carefully managed to ensure that all affected systems receive the security patch. Security teams should monitor their environments for any signs of exploitation attempts and consider implementing network-level controls to restrict access to potentially malicious Nextcloud servers. The vulnerability demonstrates the importance of proper input validation and output encoding in client applications, particularly those handling data from potentially untrusted sources. Additionally, administrators should consider implementing application whitelisting policies to further reduce the attack surface and prevent exploitation of similar vulnerabilities in other client applications.