CVE-2016-9461 in ownCloud Server
Summary
by MITRE
Nextcloud Server before 9.0.52 & ownCloud Server before 9.0.4 are not properly verifying edit check permissions on WebDAV copy actions. The WebDAV endpoint was not properly checking the permission on a WebDAV COPY action. This allowed an authenticated attacker with access to a read-only share to put new files in there. It was not possible to modify existing files.
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Analysis
by VulDB Data Team • 11/22/2022
The vulnerability identified as CVE-2016-9461 represents a critical authorization flaw in Nextcloud and ownCloud server implementations that affects versions prior to 9.0.52 and 9.0.4 respectively. This issue stems from insufficient permission validation during WebDAV copy operations, creating a privilege escalation vector that undermines the fundamental security model of these collaborative file sharing platforms. The flaw specifically targets the WebDAV endpoint's ability to properly verify edit permissions when processing copy actions, allowing malicious actors to exploit read-only access privileges for unauthorized file creation within shared directories.
The technical implementation of this vulnerability resides in the WebDAV protocol handling within the file sharing servers, where the system fails to enforce proper access control checks during copy operations. When an authenticated user with read-only permissions attempts to copy files to a shared directory, the system should validate whether the user possesses write permissions before allowing the operation. However, the flawed implementation bypasses this critical validation step, enabling attackers to place new files in read-only shares while maintaining the restriction that prevents modification of existing files. This creates a scenario where attackers can expand their influence within shared spaces without directly compromising write permissions on existing content.
From an operational impact perspective, this vulnerability exposes organizations to significant security risks as it allows attackers to establish persistent presence within shared directories through file placement. The ability to add new files to read-only shares creates potential vectors for malicious payload deployment, data exfiltration attempts, or social engineering attacks through the introduction of misleading content. The restriction that prevents modification of existing files limits the scope of damage but does not eliminate the threat entirely, as the presence of unauthorized files can compromise the integrity of shared workspaces and potentially lead to further exploitation through file execution or manipulation of shared resources. This vulnerability particularly affects collaborative environments where users may have varying levels of access control and where the integrity of shared content is paramount.
Organizations should implement immediate mitigation strategies including updating to patched versions of Nextcloud and ownCloud servers, which address the WebDAV permission validation flaw through enhanced access control checks. System administrators should also consider implementing additional monitoring of WebDAV copy operations and establishing alerts for unauthorized file placement activities within shared directories. The vulnerability aligns with CWE-284, which describes improper access control, and maps to ATT&CK technique T1078.004 for valid accounts, as it exploits legitimate authenticated access to perform unauthorized file operations. Organizations should also review their sharing policies and implement more granular permission controls to minimize the impact of such vulnerabilities, particularly in environments where sensitive data is shared across multiple user groups with varying access levels.