CVE-2015-4641 in Swiftkey Keyboard
Summary
by MITRE
Directory traversal vulnerability in the SwiftKey language-pack update implementation on Samsung Galaxy S4, S4 Mini, S5, and S6 devices allows remote web servers to write to arbitrary files, and consequently execute arbitrary code in a privileged context, by leveraging control of the skslm.swiftkey.net domain name and providing a .. (dot dot) in an entry in a ZIP archive, as demonstrated by a traversal to the /data/dalvik-cache directory.
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Analysis
by VulDB Data Team • 11/08/2024
The vulnerability CVE-2015-4641 represents a critical directory traversal flaw within the SwiftKey keyboard application's language pack update mechanism on select Samsung Galaxy devices. This weakness specifically affects Samsung Galaxy S4, S4 Mini, S5, and S6 models, creating a significant security risk that allows remote attackers to manipulate file system operations through carefully crafted malicious ZIP archives. The vulnerability stems from insufficient input validation in the update processing pipeline, where the application fails to properly sanitize file paths extracted from compressed archives before writing them to the device's file system.
The technical exploitation of this vulnerability relies on the attacker's ability to control the skslm.swiftkey.net domain, which serves as the update server for SwiftKey language packs. By crafting a malicious ZIP archive containing entries with directory traversal sequences such as "..", an attacker can manipulate the extraction process to write files to arbitrary locations within the device's file system. The demonstration of this attack shows how a traversal to the /data/dalvik-cache directory enables the execution of arbitrary code with elevated privileges, as this location typically contains system-critical components that require root-level permissions to modify. The flaw operates at the application layer, specifically within the file extraction and processing logic that handles compressed language pack updates.
The operational impact of this vulnerability extends beyond simple unauthorized file modification, as it creates a complete privilege escalation pathway that allows attackers to execute malicious code with system-level privileges. This capability transforms a remote web server compromise into a full device takeover scenario, where attackers can modify core system components, install persistent backdoors, or exfiltrate sensitive user data. The vulnerability affects devices running vulnerable versions of the SwiftKey application, making it particularly dangerous given the widespread adoption of these Samsung devices in enterprise and consumer environments. The attack vector is particularly concerning because it requires no physical access to the device and can be executed entirely through web-based interactions, making it an ideal candidate for large-scale automated attacks.
Mitigation strategies for CVE-2015-4641 should focus on immediate patching of the affected SwiftKey application versions, with Samsung releasing security updates that properly validate and sanitize file paths during ZIP archive extraction. Network-level protections can include DNS filtering to prevent resolution of the compromised skslm.swiftkey.net domain and implementing web application firewalls that can detect and block directory traversal attempts in HTTP requests. Organizations should also consider implementing mobile device management solutions that can automatically enforce application updates and monitor for suspicious file operations. From a defensive perspective, this vulnerability aligns with CWE-22 Directory Traversal and CWE-74 Improper Neutralization of Special Elements in Output Used by a Downstream Component, and maps to ATT&CK techniques including T1059 Command and Scripting Interpreter and T1068 Exploitation for Privilege Escalation. The vulnerability highlights the critical importance of input validation in mobile application security and demonstrates how seemingly innocuous update mechanisms can become attack vectors when proper security controls are not implemented.