Huawei LTE USB Stick E3372: From File Overwrite to Code Execution
In today's world, more and more devices are connected to the Internet for on-the-go connectivity. Huawei has a mobile broadband service that allows Internet connectivity via cellular networks by using a small USB dongle. The device itself – Huawei LTE USB Stick E3372 – looks like a USB thumb drive and comes with software to install on macOS called HiLink.
Any consumer laptop/computer with a USB port can be easily connected to the Internet with this USB dongle – just plug it in, install the software that comes with it, and you’re ready to go (provided the dongle has a SIM card inserted with a working data plan of course).
At the time of writing, this device can be purchased in Germany and Italy directly from Huawei:
https://consumer.huawei.com/de/routers/e3372/buy/
There are also many used and new devices available on eBay and other online retailers.
During a quick analysis of the software, I spotted a security vulnerability: one of the installed files is missing appropriate access control settings. Simply put, any authenticated user on the computer can overwrite the file:
/Library/StartupItems/MobileBrServ/mbbserviceopen.app/Contents/MacOS/mbbserviceopen
See permissions set by the installer:
This file has a special purpose: when a user logs on to the computer and inserts the dongle, that file is automatically executed to open up a web browser with the device management interface. All a malicious user needs to do is to replace the file with their own desired code and wait for a legitimate user to start using the cellular data service via Huawei device.
Product page: https://consumer.huawei.com/en/routers/e3372/specs/
The issue affects multiuser environments where one user account can execute code as another user without the latter one knowing about it. Malicious actors can take advantage of vulnerabilities like this by getting an initial foothold that triggers the installation of more robust malware.
As a part of our Responsible Disclosure policy, Trustwave SpiderLabs attempted to contact Huawei multiple times to report the vulnerability. A timeline is below.
October 7, 2020 – Initial email communication to Huawei to multiple security and support email addresses. Non-responsive to initial email communications.
December 15, 2020 – Contacted Huawei U.S. support via phone in an attempt to find the appropriate contact. We were provided a new support contact email address.
December 16, 2020 – Trustwave attempted to connect to provided email addresses multiple times. No response.
Patch Now Available
In the last 24 hours before publishing, Huawei reached out to Trustwave SpiderLabs. Huawei notified Trustwave that we did not connect with the Huawei Product Security Incident Response Team (PSIRT) email alias - PSIRT@huawei.com. Now in touch with the correct team, we provided Huawei with the pertinent information to address the vulnerability. Huawei released a patch on June 2, the day of this blog publishing. Please upgrade the affected HiLink products tool to version 22.001.34.02.03 or the latest stable version. Huawei’s security advisory can be found here: https://www.huawei.com/en/psirt/security-advisories/huawei-sa-20210602-01-permission-en
Thank you, Huawei, for providing the correct PSIRT contact information. Trustwave will use this contact information to report any future vulnerabilities moving forward.