Security Update: APEX Modules Vulnerability Fixed

Originally published at: Security Update: APEX Modules Vulnerability FIXED - Fairphone

In November 2023, a security vulnerability was detected in an assorted list of smartphones, including the Fairphone 5, by Meta Red Team X. Fairphone took immediate action to release a security fix in mid-December that solved the issue, meaning that every Fairphone model is now secured against this vulnerability.

The vulnerability detected by Meta Red Team X affects APEX modules and the way they are signed; APEX modules allow original equipment manufacturers (“OEMs”) to update specific portions of the system without issuing a full over-the-air (OTA) update, but instead only delivering the subsystems that need to be updated. These modules need to be signed with the private key of the OEM during the build process, but it was found that our building process had a shortcoming, and we were using a test key (present in the Android source code build tree) instead of Fairphone’s private key.

This means that, in practice, it would have been possible for an attacker to substitute the incorrectly signed modules with other files signed with the same test key, potentially containing malicious code. Having said that, this is not easy to exploit. The substitution would require either physical access to the device, along with root privileges, or remote access obtained through a chain of other critical vulnerabilities. Yet, it did present a high severity vulnerability.

Triggered by the report on Fairphone 5, we also opened an internal investigation on Fairphone 4 and Fairphone 3/3+, where we found similarly affected APEX modules. The vulnerability was resolved in December 2023 for all Fairphone devices with the following software versions, respectively:

  • Fairphone 5: TT3Y.A.127 (released on the 11th of December 2023)
  • Fairphone 4: TP20.C.087 (released on the 25th of December 2023)
  • Fairphone 3/3+: 6.A.023.1 (released on the 25th of December 2023)

If you have not updated your phone recently, we invite you to install the most recent software version available to you. You can always check manually for system updates in the Settings menu under the System sub-menu. More information on the vulnerability can be found on the original report or the security advisory published by Red Team X.


What does that mean for alternative OS? Do they need to integrate this fix separately from the normal Android fixes?

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