CVE-2016-4046 in OX AppSuite
Summary
by MITRE
An issue was discovered in Open-Xchange OX App Suite before 7.8.1-rev11. The API to configure external mail accounts can be abused to map and access network components within the trust boundary of the operator. Users can inject arbitrary hosts and ports to API calls. Depending on the response type, content and latency, information about existence of hosts and services can be gathered. Attackers can get internal configuration information about the infrastructure of an operator to prepare subsequent attacks.
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Analysis
by VulDB Data Team • 10/08/2022
The vulnerability identified as CVE-2016-4046 represents a critical information disclosure flaw within the Open-Xchange OX App Suite email platform prior to version 7.8.1-rev11. This security weakness resides in the application's API designed for configuring external mail accounts, which has been improperly implemented to allow unauthorized access to internal network components. The flaw enables attackers to manipulate API calls by injecting arbitrary hostnames and port numbers, effectively creating a pathway for reconnaissance activities that can reveal sensitive infrastructure details. This vulnerability operates at the intersection of insecure input validation and inadequate access controls, allowing malicious actors to map network topology and gather intelligence about internal services without proper authorization.
The technical implementation of this vulnerability stems from insufficient validation of user-supplied input within the external mail account configuration API endpoint. When users submit requests to configure external mail accounts, the system fails to properly sanitize or restrict the host and port parameters, permitting attackers to inject arbitrary network addresses. This design flaw directly relates to CWE-20, which addresses improper input validation, and CWE-22, which covers path traversal vulnerabilities. The API's response behavior creates a timing-based information disclosure mechanism where different responses for existing versus non-existing hosts reveal network topology information. Attackers can exploit this through repeated API calls with varying host parameters, observing response times and content variations to infer which services are operational within the internal network.
The operational impact of CVE-2016-4046 extends beyond simple information gathering, as it provides attackers with crucial intelligence for planning subsequent attacks against the target infrastructure. The vulnerability enables reconnaissance activities that align with techniques described in the MITRE ATT&CK framework under the reconnaissance phase, specifically T1069.002 for "Exploit Public-Facing Application" and T1082 for "System Information Discovery." By mapping internal network components, attackers can identify vulnerable services, operating systems, and network configurations that may be targeted in later attack phases. The exposure of internal infrastructure details can lead to more sophisticated attacks including privilege escalation, lateral movement, and potentially complete system compromise. Organizations using affected versions of OX App Suite face significant risk as this vulnerability can be exploited remotely without requiring authentication to the application itself.
Mitigation strategies for CVE-2016-4046 should prioritize immediate patching of affected systems to version 7.8.1-rev11 or later, which includes proper input validation and access control measures. Network administrators should implement API rate limiting and monitoring to detect anomalous request patterns that may indicate reconnaissance activities. The solution architecture must incorporate proper input sanitization and validation mechanisms that reject malformed hostnames and port specifications before processing user requests. Organizations should also establish network segmentation and access controls to limit the blast radius of potential exploitation. Security teams should deploy intrusion detection systems capable of identifying suspicious API call patterns and implement proper logging and monitoring of external mail account configuration activities. The fix should address the root cause by implementing strict validation of network parameters and preventing arbitrary host resolution within the application's trust boundary, thereby eliminating the information disclosure vector that enables attackers to map internal infrastructure components.