CVE-2017-5887 in Starscream
Summary
by MITRE
WebSocket.swift in Starscream before 2.0.4 allows an SSL Pinning bypass because pinning occurs in the stream function (this is too late; pinning should occur in the initStreamsWithData function).
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Analysis
by VulDB Data Team • 11/27/2022
The vulnerability described in CVE-2017-5887 affects the Starscream WebSocket library version 2.0.3 and earlier, specifically targeting the SSL certificate pinning mechanism implementation. This flaw represents a critical security weakness in mobile and desktop applications that rely on secure WebSocket communications. The issue stems from the improper timing of SSL certificate validation within the library's certificate pinning process, creating a window of opportunity for man-in-the-middle attacks that could compromise sensitive data transmission.
The technical flaw occurs due to the incorrect placement of SSL pinning logic within the Starscream library's codebase. The certificate pinning validation is executed in the stream function rather than in the initStreamsWithData function where it should logically occur. This timing discrepancy allows attackers to intercept the initial connection establishment phase before proper certificate validation takes place. The stream function executes after the connection has already been partially established, meaning that malicious actors can potentially establish a connection with a compromised certificate before the pinning validation occurs, effectively bypassing the intended security controls. This implementation flaw directly violates security best practices for certificate pinning and represents a clear violation of the principle of least privilege in secure communications.
The operational impact of this vulnerability is significant for any application utilizing the Starscream library for WebSocket communications. Applications that depend on certificate pinning for security assurance become vulnerable to attacks where malicious actors can establish connections with forged certificates, potentially accessing sensitive data, executing unauthorized commands, or conducting data exfiltration. The vulnerability affects the fundamental security model of applications that rely on SSL pinning as a defense mechanism against certificate authority compromise or fraudulent certificate issuance. This weakness particularly impacts mobile applications and enterprise systems where secure communication channels are critical for maintaining data integrity and confidentiality.
Organizations should immediately upgrade to Starscream version 2.0.4 or later, which addresses this timing issue in certificate pinning implementation. The fix ensures that SSL pinning validation occurs during the initial stream setup phase rather than during the stream execution phase, thereby preventing the window of vulnerability that existed in earlier versions. Security teams should conduct comprehensive code reviews to identify any custom implementations that might replicate this flawed certificate pinning pattern, as similar timing issues could exist in other libraries or custom security implementations. Additionally, organizations should implement network monitoring to detect potential certificate validation bypass attempts and consider additional security layers such as application firewalls or network segmentation to mitigate potential exploitation.
This vulnerability aligns with CWE-295 which specifically addresses improper certificate validation and represents a classic example of improper implementation of security controls. The issue also maps to ATT&CK technique T1046 which involves network service scanning, as attackers could potentially exploit this weakness to establish unauthorized connections. The timing of certificate validation in network security protocols is a critical factor in preventing man-in-the-middle attacks, and this flaw demonstrates how seemingly minor implementation details can create significant security vulnerabilities. Security practitioners should emphasize the importance of proper certificate pinning implementation timing and consider this vulnerability as a case study in how inadequate security control placement can compromise entire security architectures.