CVE-2018-14995 in Blade Vantage
Summary
by MITRE
The ZTE Blade Vantage Android device with a build fingerprint of ZTE/Z839/sweet:7.1.1/NMF26V/20180120.095344:user/release-keys, the ZTE Blade Spark Android device with a build fingerprint of ZTE/Z971/peony:7.1.1/NMF26V/20171129.143111:user/release-keys, the ZTE ZMAX Pro Android device with a build fingerprint of ZTE/P895T20/urd:6.0.1/MMB29M/20170418.114928:user/release-keys, and the ZTE ZMAX Champ Android device with a build fingerprint of ZTE/Z917VL/fortune:6.0.1/MMB29M/20170327.120922:user/release-keys contain a pre-installed platform app with a package name of com.android.modem.service (versionCode=25, versionName=7.1.1; versionCode=23, versionName=6.0.1) that exports an interface to any app on co-located on the device. Using the exported interface of the com.android.modem.service app, any app can enable and obtain certain log files (modem and logcat) without the appropriate corresponding access permissions. The modem logs contain the phone number and full text body of incoming and outgoing text messages in binary format. In addition, the modem log contains the phone numbers for both incoming and outgoing phone calls. The system-wide logcat logs (those obtained via the logcat binary) tend to contain sensitive user data. Third-party apps are prevented from directly reading the system-wide logcat logs. The capability to read from the system-wide logcat logs is only available to pre-installed system apps and platform apps. The modem log and/or logcat log, once activated, get written to external storage (SD card). An app aware of this vulnerability can enable the logs, parse them for relevant data, and exfiltrate them from the device. The modem log and logcat log are inactive by default, but a third-party app with no permissions can activate them, although the app will need to be granted the READ_EXTERNAL_STORAGE permission to access them.
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Analysis
by VulDB Data Team • 04/24/2020
The vulnerability identified as CVE-2018-14995 represents a critical security flaw in several ZTE Android devices including the Blade Vantage, Blade Spark, ZMAX Pro, and ZMAX Champ models. This vulnerability stems from a pre-installed platform application named com.android.modem.service which improperly exports an interface that allows any application installed on the same device to access sensitive modem and logcat functionality. The affected devices operate on Android versions 6.0.1 and 7.1.1, with specific build fingerprints indicating the vulnerable software configurations. The core technical issue lies in the lack of proper access controls and permission validation within the exported interface, creating an attack surface that bypasses normal Android security mechanisms.
The operational impact of this vulnerability is severe as it enables arbitrary third-party applications to access highly sensitive information without proper authorization. The modem logs contain binary representations of phone numbers and complete text message bodies for both incoming and outgoing communications, effectively providing attackers with comprehensive communication records. Additionally, these logs capture phone numbers associated with all incoming and outgoing calls, creating a detailed profile of user communication patterns. The system-wide logcat logs, which typically contain sensitive user data including personal information, application behavior details, and system-level activities, can also be accessed through this vulnerability. These logs are normally restricted to pre-installed system applications and platform apps, but the vulnerability allows any installed application to activate and read these logs, fundamentally undermining Android's permission model.
The exploitation of this vulnerability follows a specific attack pattern where malicious applications can enable logging functionality without requiring elevated privileges, then parse the collected data for sensitive information before exfiltrating it from the device. The logs are written to external storage, specifically the SD card, making them accessible to the attacker's application once the READ_EXTERNAL_STORAGE permission is granted. This vulnerability directly relates to CWE-284, which addresses improper access control, and CWE-312, concerning sensitive data exposure. From an ATT&CK framework perspective, this represents a privilege escalation technique under T1068, where an attacker gains access to system-level logging capabilities through improper interface exposure. The vulnerability also aligns with T1070, covering indicator removal and data exfiltration activities, as the collected data can be systematically harvested and transmitted.
Mitigation strategies for this vulnerability should focus on implementing proper access controls and restricting interface exposure within system applications. Device manufacturers should ensure that platform applications like com.android.modem.service only expose necessary functionality through proper permission validation and that sensitive logging capabilities require appropriate system-level permissions. Users should be advised to avoid installing untrusted applications and to regularly review application permissions, particularly those related to storage access. System administrators and security teams should monitor for unauthorized applications that might attempt to exploit this vulnerability and implement device management policies that restrict access to sensitive system interfaces. The vulnerability highlights the importance of proper privilege separation and the need for comprehensive security reviews of pre-installed system applications to prevent unauthorized access to sensitive device functionality.