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 Bla…

Summary

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.