CVE-2017-7192 in Starscream
Summary
by MITRE
WebSocket.swift in Starscream before 2.0.4 allows an SSL Pinning bypass because of incorrect management of the certValidated variable (it can be set to true but cannot be set to false).
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Analysis
by VulDB Data Team • 11/27/2022
The vulnerability identified as CVE-2017-7192 resides within the WebSocket.swift implementation of the Starscream library, a widely used Swift WebSocket client for iOS and macOS applications. This issue affects versions prior to 2.0.4 and represents a critical security flaw that undermines the fundamental security mechanism of SSL certificate pinning. The vulnerability manifests through improper handling of the certValidated variable, which is essential for validating SSL certificates during the secure connection establishment process. When an application employs SSL pinning as a security measure, it typically validates that the server presents a certificate that matches a known good certificate or public key, thereby preventing man-in-the-middle attacks and ensuring that communications occur with the intended server rather than an imposter.
The technical flaw stems from a logical error in the certificate validation logic where the certValidated variable can be set to true but cannot be reset to false when certificate validation fails. This creates a persistent state where once a certificate has been validated successfully, the application assumes all subsequent connections will maintain valid certificates regardless of whether they actually do. The vulnerability is particularly dangerous because it allows attackers to bypass certificate pinning mechanisms that are designed to protect against certificate substitution attacks. The flaw represents a classic case of improper state management and can be categorized under CWE-284, which deals with improper access control, and more specifically under CWE-310, which addresses cryptographic issues related to certificate validation. The implementation fails to properly reset the validation state, creating a condition where certificate validation becomes permanently enabled after the first successful validation.
The operational impact of this vulnerability is significant for any application that relies on SSL pinning for security. Mobile applications using the Starscream library may be vulnerable to attacks where malicious actors can intercept and manipulate communications without the application detecting the compromised connection. This bypass allows for potential data theft, session hijacking, and other man-in-the-middle attacks that would normally be prevented by proper certificate validation. The vulnerability is particularly concerning in applications handling sensitive data such as financial transactions, personal information, or corporate communications. From an adversary perspective, this flaw aligns with ATT&CK technique T1046, which involves network service scanning, and T1566, which involves credential harvesting through social engineering, as attackers can exploit the bypassed security to gain unauthorized access to protected communications.
The mitigation strategy for CVE-2017-7192 requires immediate application of the patched version 2.0.4 of the Starscream library, which properly addresses the certificate validation state management issue. Organizations should conduct thorough code reviews to identify any custom implementations that may have similar state management flaws, particularly in SSL/TLS validation logic. Security teams should also implement monitoring for unauthorized certificate changes or connection anomalies that might indicate exploitation attempts. The fix ensures that the certValidated variable can properly transition between true and false states based on actual certificate validation results, thereby restoring the intended security posture. Additionally, developers should consider implementing additional security layers such as certificate transparency monitoring and regular security assessments of third-party libraries to prevent similar issues in the future.