CVE-2018-5751 in OX AppSuite
Summary
by MITRE
The backend component in Open-Xchange OX App Suite before 7.6.3-rev36, 7.8.x before 7.8.2-rev39, 7.8.3 before 7.8.3-rev44, and 7.8.4 before 7.8.4-rev22 allows remote authenticated users to obtain sensitive information about external guest users via vectors related to the "groups" and "users" APIs.
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Analysis
by VulDB Data Team • 11/25/2025
The vulnerability identified as CVE-2018-5751 affects the Open-Xchange OX App Suite backend component and represents a significant information disclosure flaw that impacts multiple version ranges including 7.6.3-rev36, 7.8.2-rev39, 7.8.3-rev44, and 7.8.4-rev22. This vulnerability specifically targets the groups and users application programming interfaces where authenticated users can exploit the flaw to gain unauthorized access to sensitive information about external guest users within the system. The vulnerability stems from inadequate access controls and improper authorization checks within the backend API endpoints, allowing malicious actors with valid credentials to enumerate user data that should remain restricted to authorized personnel only.
The technical implementation of this vulnerability involves the backend components failing to properly validate and restrict access permissions when processing requests through the groups and users APIs. Attackers can leverage their authenticated status to make API calls that would normally be restricted to administrative or privileged users, thereby obtaining sensitive information about guest accounts including user identifiers, group memberships, and potentially other personally identifiable information. This type of flaw falls under the CWE-200 category of Information Exposure and represents a classic case of insufficient authorization checks where the system does not properly verify that the requesting user has appropriate permissions to access the requested data. The vulnerability demonstrates a fundamental breakdown in the principle of least privilege and proper access control enforcement within the application's security architecture.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can enable more sophisticated attacks including credential harvesting, social engineering campaigns, and targeted phishing attempts against external guest users. Attackers can use the leaked information to craft more convincing social engineering attacks or to identify potential targets for further exploitation. The vulnerability also represents a significant compliance risk for organizations that must maintain strict data protection standards, as unauthorized access to guest user information violates data privacy regulations and internal security policies. This flaw particularly affects organizations using Open-Xchange OX App Suite for collaboration environments where guest users are frequently invited to access shared resources, making the exposure of guest user information particularly concerning from both security and privacy perspectives.
Organizations affected by this vulnerability should immediately apply the vendor-provided patches and updates to versions 7.6.3-rev36, 7.8.2-rev39, 7.8.3-rev44, and 7.8.4-rev22 as recommended in the security advisory. System administrators should also implement additional monitoring of API access patterns to detect anomalous behavior that might indicate exploitation attempts. The mitigation strategy should include comprehensive access control reviews, implementation of proper API rate limiting, and enhanced logging of all user activities related to group and user management functions. Organizations should also consider implementing network segmentation to limit access to the backend components and establish more robust authentication mechanisms for API access. From an ATT&CK framework perspective, this vulnerability aligns with techniques related to credential access and privilege escalation, making it a critical target for both defensive and offensive security teams to address promptly.