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Re: Xamarin for Android <5.1 DLL Hijack Vulnerability


From: ValdikSS <iam () valdikss org ru>
Date: Wed, 20 May 2015 00:32:53 +0300

They don't have public bugtracker. Case ID is 140518.

On 05/20/2015 12:29 AM, Tim wrote:
Thanks for posting this to FD, these didn't even include it in their release notes;

http://developer.xamarin.com/releases/android/xamarin.android_5/xamarin.android_5.1/

Was there a bug reported in bugzilla to link back too?

-Tim Strazzere

On Tue, May 19, 2015 at 6:49 AM, ValdikSS <iam () valdikss org ru <mailto:iam () valdikss org ru>> wrote:


Xamarin for Android prior to version 5.1 allows to replace internal DLL files inside the APK with files on SD card 
which are not in a secure storage.
Malicious application without any special permissions could drop backdoored DLL files into

/storage/sdcard0/Android/data/app_id/files/.__override__/

and the victim application would use files from SD.
Not just the main application library could be hijacked, but also Xamarin's System.dll and Mono.Android.dll, which 
are shipped in all Xamarin for Android
applications.

Developers should rebuild their applications using Xamarin for Android 5.1 or newer in the release mode.

This vulnerability was found by accident, which allowed me to eat for free for a month.

Timeline:
    03.04.2015 Vulnerability is found
    07.04.2015 Message sent to Xamarin
    08.04.2015 Xamarin acknowledged the vulnerability
    29.04.2015 Fixed stable version released



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