Wallbreak

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Exploit app for CVE-2021-39670 and CVE-2021-39690, two permanent denial-of-service vulnerabilities in Android's wallpaper system

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# Wallbreak
[
Download as APK](https://github.com/Supersonic/Wallbreak/releases/download/release/Wallbreak.apk)

This app demonstrates two high severity permanent denial-of-service vulnerabilities in Android's `WallpaperManagerService` that I discovered: [CVE-2021-39670](https://www.cve.org/CVERecord?id=CVE-2021-39670) and [CVE-2021-39690](https://www.cve.org/CVERecord?id=CVE-2021-39690).
After running either exploit, the device will keep repeatedly crashing and rebooting.

Write-up coming soon! :)

## CVE-2021-39670 "Stream Exploit"

- Exploits the `setStream` API in `WallpaperManager` to exhaust device memory by setting a malicious bitmap file as the wallpaper.
- Appears to be very portable across manufacturers and device versions.
- Patch released in [May 2022 Android Security Bulletin](https://source.android.com/docs/security/bulletin/2022-05-01).
- Was [patched by](https://android.googlesource.com/platform/frameworks/base/+/b1b01433f5b8dc0702c0e1abde5f7b86b708a849) using a more efficient wallpaper decoder in `WallpaperManagerService`, and adding a file-based recovery system in case wallpaper still fails to be decoded.

## CVE-2021-39690 "Padding Exploit"

- Exploits the display padding functionality in some Android phones to either crash `SurfaceFlinger` or exhaust device memory.
- I could only reproduce this vulnerability in Pixel devices with animated live wallpapers.
- Requires Android P or higher.
- Initial patch released in [March 2022 Android Security Bulletin](https://source.android.com/docs/security/bulletin/2022-03-01).
- Was [initially patched by](https://android.googlesource.com/platform/frameworks/native/+/2914a57d755051a3e5f05154d784a08019500946) adding stricter input validation in `SurfaceFlinger`, and then [fully mitigated by](https://android.googlesource.com/platform/frameworks/base/+/f6b503a8c18a6b9179ff8d416544a6651facd805) adding a padding limit in `WallpaperManager`.

As far as I'm aware devices bricked due to these vulnerabilities *can't be fixed except through factory reset*. Please run this app at your own risk.
Note that this project is provided for educational purposes only; please don't use it for malicious activities.

Wallbreak

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