A Security Issue in Android That Remains Unfixed – Pull-down Menu On Lock Screen

Having your phone lying around when your kids are playing with everything they find is a great security test. They immediately discover new features and ways to go beyond the usual flow.

This is the way I recently discovered a security issue with Android. Apparently, even if the phone is locked, the pull-down menu with quick settings works. Also, volume control works. Not every functionality inside the quick settings menu works fully while unlocked, but you can disable mobile data and Wi-Fi, you can turn on your hotspot, you can switch to Airplane mode.

While this has been pointed out on Google Pixel forums, on reddit and Stack Exchange, it has not been fixed in stock Android. Different manufacturers seem to have acknowledged the issue in their custom ROMs, but that’s not a reliable long-term solution.

Let me explain why this is an issue. First, it breaks the assumption that when the phone is locked nothing works. Breaking user assumptions is bad by itself.

Second, it allows criminals to steal your phone and put in in Airplane mode, thus disabling any ability to track the phone – either through “find my phone” services, or by the police through mobile carriers. They can silence the phone, so that it’s not found with “ring my phone” functionality. It’s true that an attacker can just take out the SIM card, but having the Wi-Fi on still allows tracking using wifi networks through which the phone passes.

Third, the hotspot (similar issues go with Bluetooth). Allowing a connection can be used to attack the device. It’s not trivial, but it’s not impossible either. It can also be used to do all sorts of network attacks on other devices connected to the hotspot (e.g. you enable the hotspot, a laptop connects automatically, and you execute an APR poisoning attack). The hotspot also allows attackers to use a device to commit online crimes and frame the owner. Especially if they do not steal the phone, but leave it lying where it originally was, just with the hotspot turned on. Of course, they would need to get the password for the hotspot, but this can be obtained through social engineering.

The interesting thing is that when you use Google’s Family Link to lock a device that’s given to a child, the pull-down menu doesn’t work. So the basic idea that “once locked, nothing should be accessible” is there, it’s just not implemented in the default use-case.

While the things described above are indeed edge-cases and may be far fetched, I think they should be fixed. The more functionality is available on a locked phone, the more attack surface it has (including for the exploitation of 0days).

3 thoughts on “A Security Issue in Android That Remains Unfixed – Pull-down Menu On Lock Screen”

  1. You are totally right about that, especially on the attack surface part.
    AOSP would only have to adopt what GraphenOS already implemented, as GrapheneOS does not allow interaction with the Pull-Down Menue.

  2. Hi Bozhidar, your post made us think to take two features from our Cerberus Anti-theft service and create an app called Cerberus Lock Screen Protector. It can block the quick settings and power menu from the lock screen, it is free, with no ads and does not collect any data – besides anonymous data from Firebase Analytics/Crashlytics to improve performance.
    I apologize for the shameless plug, but in case you are interested you can install it from here: https://play.google.com/store/apps/details?id=com.lsdroid.lsp

  3. I used to hide the Airplane and Mobile data tiles from this menu. So, leaving no option to turn off mobile data with an e-Sim could ease things.
    But now, the Mobile Data tile was replaced by the new Internet tile (mobile data and wifi in one space) making it harder to choose between having an easy access to Wifi networks or staying safer against theft.
    Some people discovered a temporary way to bring back the old tiles using ADB, but a simple reset will undo this solution.
    Luckily, I found this amazing app called Cerberus that tries its best to fully lock the phone if the pull-down menu or the power menu are used on the locked screen, making it very difficult for the thief to use it. The downside for me is that the Flashlight tile is now only usable with the screen unlocked. Anyways, this is a minor problem.

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