Researchers recently discovered 2 new critical vulnerabilities in the SHAREit App lets attackers bypass the Android device authentication mechanism and download the arbitrary files in victims device.

SHAREit is data sharing cross-platform application for Android, iOS, PC & Mac and the app downloaded by nearly 500 Million users since 2013 when the app was launched.

SHAREit mainly using 2 Command Channel (Port 55283), Download Channel (Port 2999) different channel to communicate the devices and share the data with each other.

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Command channel is a regular TCP channel that help to communicate 2 devices each other using raw socket connections including connection health check, handling the file Transfer request.

Download channel implemented its own HTTP server by SHAREit that helps clients to download the received files in another end.

SHAREit App Vulnerabilities

The first vulnerability in the SHAREit app <= v 4.0.38 allows attackers to download the authenticated arbitrary file dues to improper validation in msgid, a unique identifier for each request to make sure that download request was originally initiated by the sender.

In this case, whenever the user initiated the download request from the SHAREit app then the SHAREit client will send the GET request to the HTTP server. here how it looks link,

http://shareit_sender_ip:2999/download?metadatatype=photo&metadataid=1337&filetype=thumbnail&msgid=c60088c13d6

Above link contains a 4 different parameter and identifier, each has its own operation including to defines what resource we are trying to download (metadatatype), representing asset id in Android MediaStore ( metdataid) , define the Preview of the resource (filetype ) and each request to make sure that download request was originally initiated by the sender( msgid ).

Here the interesting part is that the application fails to validate msgid parameter that allows a malicious client with a valid session to download any resource by directly referencing its identifier.

In this case, sometimes getting a valid session would trigger the alarms when they see unusual session and limiting that would decrease success rate. so here we move to second vulnerability.

Authentication bypass, a Second vulnerability allows SHAREit <= v4.0.34 exhibited a very odd behavior that lead to bypass the device authentication.

During the exploitation Phase, to have the exact path of the target file leads to easily exploit the device and download the files but its not a usual case.

In this case, two( SHAREit History, SHAREit MediaStore Database) distinct database files related to SHAREit application may be useful to make the exploitation easy.

Here SHAREit MediaStore database containing interesting information about files in the system including file name, type, size, path and more other information.

According to Redforce research, We created a base exploit toolkit which we used to create two distinct proofs of a concept dubbed “DUMPit!”, one with a user-friendly GUI that enables you to choose your target and what information you want to fetch, and an auto-pwn module where it automatically detects SHAREit or open WiFi networks.

Here the proof-of-concept video for SHAREit remote file download with authentication bypass.

This vulnerability was originally discovered on back to December 2017 and the silent fix was done but SHAREit team refusing to disclose the exact patched version nor assign CVE numbers to discovered vulnerabilities. Exploit can be downloaded from thisGitHub repository.

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