CVE-2017-9586 in Mobile Banking App
Summary
by MITRE
The "FSBY Mobile Banking" by First State Bank of Yoakum TX app 3.0.0 -- aka fsby-mobile-banking/id899136434 for iOS does not verify X.509 certificates from SSL servers, which allows man-in-the-middle attackers to spoof servers and obtain sensitive information via a crafted certificate.
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Analysis
by VulDB Data Team • 10/18/2019
The CVE-2017-9586 vulnerability affects the FSBY Mobile Banking application version 3.0.0 for iOS devices, representing a critical security flaw in the mobile banking ecosystem. This vulnerability stems from the application's failure to properly validate X.509 certificates during SSL/TLS connections, creating a significant attack surface that adversaries can exploit to compromise user data and financial transactions. The flaw exists within the certificate verification mechanism that should normally ensure the authenticity and integrity of server certificates presented during secure communications between the mobile client and banking servers.
The technical implementation of this vulnerability allows attackers to perform man-in-the-middle attacks by presenting fraudulent SSL certificates that appear legitimate to the vulnerable application. When the FSBY Mobile Banking app establishes a secure connection to its backend servers, it fails to validate the certificate chain against trusted Certificate Authorities, enabling attackers to intercept and manipulate encrypted communications. This weakness directly violates fundamental security principles of secure communication and authentication, as outlined in the OWASP Mobile Security Project's top ten vulnerabilities and aligns with CWE-295 which specifically addresses improper certificate validation.
The operational impact of this vulnerability is severe for both end users and the financial institution. Mobile banking users face substantial risk of credential theft, financial transaction manipulation, and unauthorized access to their banking accounts when communicating with compromised servers. Attackers can exploit this vulnerability to capture sensitive information including account numbers, login credentials, and transaction details without the user's knowledge. The attack vector is particularly dangerous because it operates at the transport layer security level, meaning that even if users believe they are communicating securely with their bank, they may actually be communicating with an attacker's server that simply mimics the legitimate banking infrastructure.
This vulnerability demonstrates a critical failure in mobile application security implementation that aligns with several ATT&CK framework techniques including T1046 for network service scanning and T1566 for credential harvesting through social engineering and network attacks. The lack of proper certificate pinning and validation creates an environment where attackers can easily establish fraudulent secure connections that appear legitimate to users. Organizations should implement certificate pinning mechanisms, enforce strict certificate validation procedures, and regularly audit their mobile applications for similar security flaws. The vulnerability also highlights the importance of following industry standards such as NIST SP 800-52 for certificate management and the TLS protocol requirements that mandate proper certificate validation to prevent such attacks. Financial institutions must ensure their mobile applications implement robust security controls including certificate transparency, certificate pinning, and regular security assessments to prevent similar vulnerabilities from compromising user data and institutional security.