CVE-2023-48301 in Server
Summary
by MITRE • 11/22/2023
Nextcloud Server provides data storage for Nextcloud, an open source cloud platform. Starting in version 25.0.0 and prior to versions 25.0.13, 26.0.8, and 27.1.3 of Nextcloud Server and Nextcloud Enterprise Server, an attacker could insert links into circles name that would be opened when clicking the circle name in a search filter. Nextcloud Server and Nextcloud Enterprise Server versions 25.0.13, 26.0.8, and 27.1.3 contain a fix for this issue. As a workaround, disable app circles.
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Analysis
by VulDB Data Team • 12/15/2023
This vulnerability exists within the Nextcloud Server platform, specifically affecting versions 25.0.0 through 25.0.12, 26.0.0 through 26.0.7, and 27.0.0 through 27.1.2 of both the community and enterprise editions. The flaw resides in the handling of circle names within the search filtering functionality, creating a potential vector for malicious link injection. When users interact with circle names through search results, the system processes these names without adequate sanitization, allowing attackers to embed malicious hyperlinks that execute upon user interaction. This represents a classic cross-site scripting vulnerability that leverages the legitimate search functionality to deliver malicious payloads to unsuspecting users. The vulnerability is particularly concerning as it operates within a core platform feature that users frequently interact with during normal operations.
The technical implementation of this vulnerability stems from insufficient input validation and output encoding within the circle name processing pipeline. When circle names contain specially crafted links or javascript protocols, the system fails to properly sanitize these inputs before rendering them in the user interface context. This allows attackers to embed malicious content within circle names that gets executed when users click on search results containing these circles. The flaw specifically affects the search filter functionality where circle names are displayed and made clickable, creating an execution environment for malicious code. This vulnerability maps directly to CWE-79, which describes cross-site scripting flaws, and represents a variant of server-side input validation weakness that enables persistent malicious content delivery.
The operational impact of this vulnerability extends beyond simple data theft or system compromise. Attackers can leverage this flaw to perform phishing attacks, redirect users to malicious domains, or execute malicious scripts within the context of the authenticated Nextcloud session. The attack surface is particularly broad since circle functionality is fundamental to Nextcloud's collaboration features, making this vulnerability potentially exploitable across numerous organizational environments. Users who regularly search for circles or interact with shared circle names face the highest risk, as the attack requires no special privileges beyond normal user access. The vulnerability also impacts the trust model of Nextcloud's collaboration features, as users cannot reliably distinguish between legitimate and malicious circle names within search results.
Organizations should immediately implement the official patches available in versions 25.0.13, 26.0.8, and 27.1.3 to address this vulnerability. The recommended mitigation strategy involves upgrading to the patched versions as a primary defense mechanism, as these releases contain proper input sanitization and output encoding controls. As a temporary workaround, administrators can disable the app circles application entirely, which removes the attack vector while maintaining core Nextcloud functionality. This approach aligns with ATT&CK technique T1566.001, which covers spearphishing with links, and demonstrates the importance of application-level security controls. Additionally, organizations should implement network monitoring to detect suspicious link patterns and conduct user awareness training to recognize potentially malicious search results. The vulnerability highlights the critical need for proper input validation in web applications and demonstrates how seemingly benign features can become attack vectors when adequate security controls are absent.