CVE-2016-5876 in ownCloud
Summary
by MITRE
ownCloud server before 8.2.6 and 9.x before 9.0.3, when the gallery app is enabled, allows remote attackers to download arbitrary images via a direct request.
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Analysis
by VulDB Data Team • 05/14/2026
The vulnerability identified as CVE-2016-5876 represents a critical access control flaw within the ownCloud server platform that affects versions prior to 8.2.6 and 9.0.3. This security issue specifically targets the gallery application component which is commonly used for image management and display within the ownCloud ecosystem. The vulnerability arises from insufficient authorization checks that permit unauthenticated or unauthorized users to bypass normal access controls and directly request image files from the server. The flaw exists in the gallery app's implementation where it fails to properly validate user permissions before serving image content, creating a path for malicious actors to access files they should not be able to retrieve.
The technical nature of this vulnerability aligns with CWE-285, which addresses insufficient authorization issues in software systems. Attackers can exploit this weakness by crafting direct HTTP requests to specific image endpoints within the gallery application, bypassing the normal authentication and authorization mechanisms that should protect sensitive content. This type of vulnerability falls under the ATT&CK framework category of privilege escalation and credential access, as it allows unauthorized parties to obtain access to files that would normally require proper authentication. The flaw essentially creates a backdoor path through which any remote attacker can retrieve images without proper credentials, potentially exposing personal photos, documents, or other sensitive visual content stored within the ownCloud environment.
The operational impact of CVE-2016-5876 extends beyond simple data exposure, as it can lead to significant privacy violations and potential data breaches within organizations using ownCloud services. When the gallery app is enabled, users typically expect that their image collections are protected by the platform's authentication system, but this vulnerability undermines that security model entirely. The consequences can be particularly severe for businesses or individuals who store confidential or personal images within the system, as attackers can systematically download collections of files without detection. Organizations may experience reputational damage, regulatory compliance violations, and potential legal ramifications depending on the nature of the exposed content.
Mitigation strategies for CVE-2016-5876 require immediate implementation of software updates to versions 8.2.6 or 9.0.3 where the vulnerability has been patched. System administrators should also consider implementing additional network-level controls such as web application firewalls that can detect and block suspicious direct image requests. The patch addresses the core authorization flaw by implementing proper access control checks before serving gallery images, ensuring that only authenticated users with appropriate permissions can retrieve content. Organizations should conduct comprehensive security audits of their ownCloud installations to verify that all gallery app configurations are properly secured and that no other similar vulnerabilities exist within the platform. Regular security monitoring and vulnerability assessment procedures should be implemented to detect and remediate similar issues before they can be exploited by malicious actors in the future.