An issue was discovered in KaiOS 3.0 before 3.1. The /system/bin/tctweb_server binary exposes a local web server that responds to GET and POST requests on port 2929. The server accepts arbitrary Bash commands and executes them as root. Because it is not permission or context restricted and returns proper CORS headers, it's accessible to all websites via the browser. At a bare minimum, this allows an attacker to retrieve a list of the user's installed apps, notifications, and downloads. It also allows an attacker to delete local files and modify system properties including the boolean persist.moz.killswitch property (which would render the device inoperable). This vulnerability is partially mitigated by SELinux which prevents reads, writes, or modifications to files or permissions within protected partitions.

An issue was discovered in KaiOS 3.0 and 3.1. The binary /system/kaios/api-daemon exposes a local web server on *.localhost with subdomains for each installed applications, e.g., myapp.localhost. An attacker can make fetch requests to api-deamon to determine if a given app is installed and read the manifest.webmanifest contents, including the app version.

An issue was discovered in KaiOS 3.0. The pre-installed Communications application exposes a Web Activity that returns the user's call log without origin or permission checks. An attacker can inject a JavaScript payload that runs in a browser or app without user interaction or consent. This allows an attacker to send the user's call logs to a remote server via XMLHttpRequest or Fetch.