CVE-2017-5866 in ownCloud Server
Summary
by MITRE
The autocomplete feature in the E-Mail share dialog in ownCloud Server before 8.1.11, 8.2.x before 8.2.9, 9.0.x before 9.0.7, and 9.1.x before 9.1.3 allows remote authenticated users to obtain sensitive information via unspecified vectors.
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Analysis
by VulDB Data Team • 09/04/2020
The vulnerability identified as CVE-2017-5866 represents a sensitive information disclosure flaw within the email share dialog functionality of ownCloud Server versions prior to specific patch releases. This issue affects multiple major versions including 8.1.10 and earlier, 8.2.8 and earlier, 9.0.6 and earlier, and 9.1.2 and earlier, creating a widespread impact across the ownCloud ecosystem. The vulnerability specifically resides in the autocomplete feature of the email share dialog, which is a commonly used function for sharing files and folders with other users via email addresses.
The technical nature of this vulnerability stems from insufficient input validation and output sanitization within the email autocomplete functionality. When authenticated users interact with the email share dialog, the system's autocomplete feature attempts to suggest email addresses based on user input or existing contacts. However, the implementation fails to properly restrict or sanitize the data returned during autocomplete operations, allowing malicious users to potentially extract information about other users within the system. This type of vulnerability falls under the category of information disclosure, where unauthorized data exposure occurs through legitimate system functionality.
The operational impact of CVE-2017-5866 extends beyond simple data leakage, as it can enable attackers to enumerate valid user accounts and potentially map out the user base of an organization using ownCloud services. This information can serve as a foundation for further attacks including credential stuffing, social engineering campaigns, or targeted phishing attempts. The vulnerability's classification aligns with CWE-200, which addresses "Information Exposure," and can be mapped to ATT&CK technique T1087.001 for "Account Discovery" through the enumeration of user accounts. Attackers could leverage this information to conduct more sophisticated attacks targeting specific user accounts or to build comprehensive user directories for abuse.
Organizations utilizing affected ownCloud versions should prioritize immediate patching to remediate this vulnerability. The recommended mitigation strategy involves upgrading to the patched versions 8.1.11, 8.2.9, 9.0.7, and 9.1.3 respectively. Additionally, administrators should implement network-level monitoring to detect unusual patterns in email sharing activities and consider implementing additional access controls or rate limiting for email share functionality. Security teams should also conduct thorough assessments of their ownCloud implementations to identify any other potential information disclosure vectors and ensure proper input validation across all user-facing interfaces. The vulnerability demonstrates the importance of securing all user interaction points, particularly those involving data auto-completion features that may inadvertently expose system information to authenticated users.