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Researchers have discovered vulnerabilities in the SHAREit app which could allow attackers to bypass device authentication and steal files containing sensitive information.
SHAREit is a popular file sharing application for Android, iOS, Windows and Mac which can help people share video, music, files, and apps. With more than 500 million users, it was found vulnerable to a file transfer authentication bypass and an arbitrary file download vulnerability, according to a blog post.
The researchers decided not to disclose their details until Monday “given the impact of the vulnerability, its big attack surface and ease of exploitation.”
“We wanted to give as many people as we can the time to update and patch their devices before disclosing such critical vulnerability,” said Abdulrahman Nour, a security engineer at RedForce.
The File Transfer Process
SHAREit server hosts multiple services via different ports on a device, but the researchers analyzed two designated services including Command Channel (runs on Port 55283) and Download Channel (runs on Port 2999).
When you use the SHAREit Android app to send a file to the other device, a regular file transfer session starts with a regular device identification, then the ‘sender’ sends a control message to the ‘receiver,’ indicating that you have a file to share.
Once the ‘receiver’ verifies that the file is not duplicate, it goes to Download Channel and fetches the sent file using information from the previous control message.
Files Can Be Accessed Using The Flaw
Researchers discovered that when a user tries to fetch a non-existing page, instead of a regular 404 page, the app responds with a 200 status code empty page and adds the user into recognized devices, eventually authenticating an unauthorized user.
A fully functional proof-of-concept exploit for this SHAREit flaw would be as simple as curl http://shareit_sender_ip:2999/DontExist, making it the weirdest and simplest authentication bypass ever.
Researchers also found that when a download request is initiated, SHAREit client sends a GET request to the sender’s HTTP server, which looks like the following URL:
The flaws could be exploited by an attacker on a shared WiFi network, and unfortunately vulnerable SHAREit versions create an easily distinguished open Wi-Fi hotspot which one can use not only to intercept traffic (since it uses HTTP) between the two devices, but also to exploit the discovered vulnerabilities and have unrestricted access to vulnerable device storage.
To overcome this, researchers started looking for files with known paths that are already publicly available, including SHAREit History and SHAREit MediaStore Database, which may contain interesting information.
“There are other files that contain juicy information such as user’s Facebook token, Amazon Web Service user’s key, auto-fill data and cookies of websites visited using SHAREit webview and even the plaintext of user’s original hotspot (the application stores it to reset the hotspot settings to original values) and much more,” researchers said.
Using their proof-of-concept exploit dubbed DUMPit!, the researchers managed to download nearly 3000 unique files having around 2GBs in less than 8 minutes of file transfer session.
The team contacted the SHAREit Team multiple times over multiple platforms in early January 2018 but got no response until early February when the researchers warned the company to release the vulnerability details to the public after 30 days.
“Communication with SHAREit team was not a good experience at all; Not only they took too long to respond to our messages, they also were not cooperative in any means, and we did not feel that our work or efforts were appreciated at all,” researchers said.
After giving enough time to users to update their SHAREit app, researchers have now released technical details of the vulnerabilities, along with the PoC exploit, DUMBit!, which can be downloaded from the GitHub website.