CVE-2023-38295

Certain software builds for the TCL 30Z and TCL 10 Android devices contain a vulnerable, pre-installed app that relies on a missing permission that provides no protection at runtime. The missing permission is required as an access permission by components in various pre-installed apps. On the TCL 30Z device, the vulnerable app has a package name of com.tcl.screenrecorder (versionCode=1221092802, versionName=v5.2120.02.12008.1.T ; versionCode=1221092805, versionName=v5.2120.02.12008.2.T). On the TCL 10L device, the vulnerable app has a package name of com.tcl.sos (versionCode=2020102827, versionName=v3.2014.12.1012.B). When a third-party app declares and requests the missing permission, it can interact with certain service components in the aforementioned apps (that execute with system privileges) to perform arbitrary files reads/writes in its context. An app exploiting this vulnerability only needs to declare and request the single missing permission and no user interaction is required beyond installing and running a third-party app. The software build fingerprints for each confirmed vulnerable device are as follows: TCL 10L (TCL/T770B/T1_LITE:11/RKQ1.210107.001/8BIC:user/release-keys) and TCL 30Z (TCL/4188R/Jetta_ATT:12/SP1A.210812.016/LV8E:user/release-keys, TCL/T602DL/Jetta_TF:12/SP1A.210812.016/vU5P:user/release-keys, TCL/T602DL/Jetta_TF:12/SP1A.210812.016/vU61:user/release-keys, TCL/T602DL/Jetta_TF:12/SP1A.210812.016/vU66:user/release-keys, TCL/T602DL/Jetta_TF:12/SP1A.210812.016/vU68:user/release-keys, TCL/T602DL/Jetta_TF:12/SP1A.210812.016/vU6P:user/release-keys, and TCL/T602DL/Jetta_TF:12/SP1A.210812.016/vU6X:user/release-keys). This malicious app declares the missing permission named com.tct.smart.switchphone.permission.SWITCH_DATA as a normal permission, requests the missing permission, and uses it to interact with the com.tct.smart.switchdata.DataService service component that is declared in vulnerable apps that execute with system privileges to perform arbitrary file reads/writes.

Weakness

During installation, installed file permissions are set to allow anyone to modify those files.

Potential Mitigations

• Compartmentalize the system to have “safe” areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area.
• Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide the appropriate time to use privileges and the time to drop privileges.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/1.html
• https://cwe.mitre.org/data/definitions/127.html
• https://cwe.mitre.org/data/definitions/81.html

References

• https://media.defcon.org/DEF%20CON%2031/DEF%20CON%2031%20presentations/Ryan%20Johnson%20Mohamed%20Elsabagh%20Angelos%20Stavrou%20-%20Still%20Vulnerable%20Out%20of%20the%20Box%20Revisiting%20the%20Security%20of%20Prepaid%20Android%20Carrier%20Devices.pdf