CVE-2015-4640 in Galaxy S4
Summary
by MITRE
The SwiftKey language-pack update implementation on Samsung Galaxy S4, S4 Mini, S5, and S6 devices relies on an HTTP connection to the skslm.swiftkey.net server, which allows man-in-the-middle attackers to write to language-pack files by modifying an HTTP response. NOTE: CVE-2015-4640 exploitation can be combined with CVE-2015-4641 exploitation for man-in-the-middle code execution.
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Analysis
by VulDB Data Team • 11/08/2024
The vulnerability described in CVE-2015-4640 represents a critical security flaw in the SwiftKey keyboard application's language pack update mechanism on select Samsung Galaxy devices. This weakness stems from the application's reliance on unencrypted HTTP connections to communicate with the skslm.swiftkey.net server during language pack updates. The implementation fails to properly validate or authenticate the communication channel, creating an exploitable condition that allows attackers positioned within the network traffic path to intercept and manipulate the update process. The vulnerability specifically affects Samsung Galaxy S4, S4 Mini, S5, and S6 devices, indicating a widespread impact across multiple generations of popular smartphones. The flaw demonstrates a fundamental failure in secure communication implementation, where the absence of proper transport layer security leaves the update mechanism susceptible to active network attacks.
The technical implementation of this vulnerability occurs through a man-in-the-middle attack vector that exploits the lack of encryption and authentication in the HTTP communication channel. When the SwiftKey application attempts to download language pack updates, it establishes an HTTP connection to the remote server without implementing certificate validation or secure transport protocols. Attackers can intercept these HTTP requests and modify the responses to include malicious content that gets written to the language pack files on the device. This modification process effectively allows attackers to inject arbitrary code or data into the language pack update mechanism, potentially compromising the device's security posture. The vulnerability operates at the network level, requiring attackers to be positioned between the device and the update server, making it particularly concerning for users on public Wi-Fi networks or compromised networks.
The operational impact of CVE-2015-4640 extends beyond simple data manipulation, as the vulnerability can be combined with CVE-2015-4641 to achieve full code execution capabilities. This combination creates a powerful attack chain where the initial man-in-the-middle manipulation of language pack files can be leveraged to achieve more severe consequences. The language pack update functionality typically runs with elevated privileges, making successful exploitation potentially dangerous for device security. Attackers could potentially use this vulnerability to install malicious language packs that execute code when the keyboard application processes them, effectively creating a persistent backdoor on the device. The combination with CVE-2015-4641 demonstrates how seemingly isolated vulnerabilities can create cascading security issues when exploited together, highlighting the importance of comprehensive vulnerability assessment and remediation strategies.
Security practitioners should recognize this vulnerability as a clear violation of secure coding practices and network security principles. The flaw aligns with common weakness enumerations such as CWE-319, which addresses the exposure of sensitive information through improper use of network communication, and CWE-310, which covers cryptographic weaknesses in communication protocols. From an attack framework perspective, this vulnerability maps to the MITRE ATT&CK technique T1059.007 for command and control communication and T1071.004 for application layer protocol usage. Organizations should implement immediate mitigations including network monitoring for suspicious traffic patterns, deployment of network segmentation to prevent man-in-the-middle attacks, and enforcement of secure communication protocols. Device manufacturers and users should prioritize firmware updates and security patches, while network administrators should consider implementing additional security controls such as SSL inspection and network access controls to prevent exploitation of this vulnerability across their environments.