CVE-2015-4456 in Desktop Client
Summary
by MITRE
ownCloud Desktop Client before 1.8.2 does not call QNetworkReply::ignoreSslErrors with the list of errors to be ignored, allows man-in-the-middle attackers to bypass the user's certificate distrust decision and obtain sensitive information by leveraging a self-signed certificate and a connection to a server using its own self-signed certificate.
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Analysis
by VulDB Data Team • 11/24/2024
The vulnerability identified as CVE-2015-4456 affects the ownCloud Desktop Client version 1.8.1 and earlier, representing a critical security flaw in the client's SSL/TLS certificate validation implementation. This issue stems from the client's improper handling of SSL certificate errors during network communications, specifically within the Qt-based networking framework. The vulnerability allows attackers to perform man-in-the-middle attacks by exploiting the client's failure to properly validate SSL certificates, particularly when connecting to servers that utilize self-signed certificates.
The technical root cause of this vulnerability lies in the client's implementation of QNetworkReply::ignoreSslErrors function, which is a Qt networking API call designed to handle SSL certificate validation errors. When the ownCloud client connects to a server, it should present the user with certificate validation errors and allow them to make an informed decision about trusting the certificate. However, the vulnerable version fails to pass the specific list of SSL errors to ignoreSslErrors, effectively bypassing the user's certificate distrust decision. This improper implementation means that when a self-signed certificate is presented, the client automatically accepts it without user confirmation, creating a security hole that can be exploited by malicious actors.
The operational impact of this vulnerability is significant, as it enables attackers to conduct successful man-in-the-middle attacks against users of the ownCloud client. An attacker positioned between the client and the server can intercept communications by presenting a self-signed certificate that mimics the legitimate server. Since the client automatically accepts the certificate without user interaction, sensitive information such as authentication credentials, file contents, and user data can be intercepted and potentially modified during transmission. This vulnerability directly violates the fundamental security principle of certificate validation and trust, undermining the integrity of the encrypted communication channel that users expect to maintain.
This vulnerability maps to CWE-295, which describes "Improper Certificate Validation," and aligns with ATT&CK technique T1041, which covers "Exfiltration Over C2 Channel." The flaw represents a critical failure in the client's secure communication implementation, where the application fails to properly validate SSL certificates and instead automatically accepts potentially malicious certificates. The impact extends beyond simple data interception to include potential credential theft, data manipulation, and unauthorized access to user files stored on the ownCloud server. Organizations using the vulnerable client version face heightened risk of data breaches and unauthorized access to sensitive information, particularly in environments where network traffic may be monitored or intercepted by malicious actors.
The recommended mitigation for this vulnerability involves upgrading to ownCloud Desktop Client version 1.8.2 or later, which properly implements the QNetworkReply::ignoreSslErrors function with appropriate error handling. System administrators should also implement network monitoring to detect unusual certificate behavior and ensure that users are aware of the security implications of accepting self-signed certificates. Additionally, organizations should consider implementing certificate pinning mechanisms or using properly signed certificates from trusted certificate authorities to further reduce the attack surface. The vulnerability demonstrates the critical importance of proper SSL certificate validation in client applications and highlights the need for thorough security testing of cryptographic implementations in desktop software.