CVE-2020-5523 in App
Summary
by MITRE
Android App 'MyPallete' and some of the Android banking applications based on 'MyPallete' do not verify X.509 certificates from servers, and also do not properly validate certificates with host-mismatch, 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 • 03/27/2024
The vulnerability identified as CVE-2020-5523 affects Android applications built upon the MyPallete framework, specifically targeting mobile banking applications that utilize this underlying technology. This represents a critical security flaw in the certificate validation mechanisms implemented within these mobile financial applications. The vulnerability stems from improper implementation of SSL/TLS certificate verification processes, which creates a significant attack surface for malicious actors seeking to compromise user financial data and sensitive information.
The technical flaw manifests in two primary areas of certificate validation failure. First, the applications fail to properly verify X.509 certificates presented by servers during the secure communication establishment process. This omission allows attackers to present fraudulent certificates without detection, bypassing the fundamental security mechanism designed to ensure server authenticity. Second, the applications demonstrate inadequate handling of certificate host mismatches, where the certificate subject does not match the expected server hostname. This weakness enables man-in-the-middle attacks where attackers can successfully impersonate legitimate banking servers by presenting certificates that appear valid but are actually crafted to deceive the application's validation logic.
The operational impact of this vulnerability extends beyond simple data interception, as it fundamentally undermines the trust model that secure financial transactions depend upon. Attackers exploiting this vulnerability can establish fraudulent secure connections with users' mobile devices, enabling them to capture sensitive banking credentials, transaction details, and personal financial information. The implications are particularly severe for banking applications where users expect end-to-end encryption and server authentication to protect their financial data. This vulnerability directly maps to CWE-295, which addresses "Improper Certificate Validation," and aligns with ATT&CK technique T1041, "Exfiltration Over C2 Channel," as compromised applications could facilitate data exfiltration from infected devices.
The attack vector for this vulnerability involves network-based interception where malicious actors position themselves between users and legitimate banking servers. Through techniques such as DNS spoofing or network interception, attackers can present forged certificates that appear legitimate to the vulnerable applications. The lack of proper certificate validation means that users receive no warning when communicating with fraudulent servers, creating a false sense of security while their financial data is being compromised. This vulnerability is particularly dangerous in environments where users access banking services over unsecured networks such as public wifi, where such interception attacks are more easily executed.
Mitigation strategies for this vulnerability require immediate attention from application developers and security teams. The primary remediation involves implementing proper certificate pinning mechanisms that validate certificate chains against known good certificates or public key fingerprints. Applications should enforce strict hostname validation to ensure certificate subjects match expected server names, preventing host mismatch attacks. Additionally, developers must implement robust certificate validation routines that check certificate expiration dates, issuer authenticity, and certificate revocation status. Security teams should also consider implementing network-level protections such as deep packet inspection and certificate transparency monitoring to detect and prevent exploitation attempts. Regular security audits and code reviews focusing on cryptographic implementation practices are essential to prevent similar vulnerabilities in future application development cycles.