Same problem here for keepass2 2.36+dfsg-1 on up-to-date Ubuntu 17.10. Note that Windows key was used in combination with an arrow key to reposition the window at half width on one side of the screen. That is how to reproduce this. $ keepass2 Stacktrace: at <0xffffffff> at (wrapper managed-to-native) System.Windows.Forms.X11Keyboard.Xutf8LookupString (intptr,System.Windows.Forms.XEvent&,byte[],int,intptr&,System.Windows.Forms.XLookupStatus&) <0x000a4> at System.Windows.Forms.X11Keyboard.LookupString (System.Windows.Forms.XEvent&,int,System.Windows.Forms.XKeySym&,System.Windows.Forms.XLookupStatus&) <0x000c3> at System.Windows.Forms.X11Keyboard.EventToVkey (System.Windows.Forms.XEvent) <0x0003f> at System.Windows.Forms.X11Keyboard.ToUnicode (int,int,string&) <0x0035f> at System.Windows.Forms.X11Keyboard.TranslateMessage (System.Windows.Forms.MSG&) <0x00127> at System.Windows.Forms.XplatUIX11.TranslateMessage (System.Windows.Forms.MSG&) <0x00027> at System.Windows.Forms.XplatUI.TranslateMessage (System.Windows.Forms.MSG&) <0x00024> at System.Windows.Forms.Application.RunLoop (bool,System.Windows.Forms.ApplicationContext) <0x00da7> at System.Windows.Forms.Application.Run (System.Windows.Forms.ApplicationContext) <0x0005b> at System.Windows.Forms.Application.Run (System.Windows.Forms.Form) <0x00037> at KeePass.Program.Main (string[]) <0x00e0b> at (wrapper runtime-invoke) .runtime_invoke_void_object (object,intptr,intptr,intptr) <0x000d1> Native stacktrace: /usr/bin/cli(+0xc8514) [0x55a1ef180514] /usr/bin/cli(+0x1217ce) [0x55a1ef1d97ce] /usr/bin/cli(+0x3d7e3) [0x55a1ef0f57e3] /lib/x86_64-linux-gnu/libpthread.so.0(+0x13150) [0x7f9a9ee16150] /lib/x86_64-linux-gnu/libc.so.6(+0xa8476) [0x7f9a9e8b4476] /usr/lib/x86_64-linux-gnu/libX11.so.6(_XimLocalUtf8LookupString+0xde) [0x7f9a9a9aa7ee] [0x409f0b45] Debug info from gdb: [New LWP 14878] [New LWP 14879] [New LWP 14885] [New LWP 14886] [New LWP 14887] [New LWP 14888] [New LWP 14890] [New LWP 14891] [New LWP 14892] [Thread debugging using libthread_db enabled] Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1". 0x00007f9a9ee15a4a in waitpid () from /lib/x86_64-linux-gnu/libpthread.so.0 Id Target Id Frame * 1 Thread 0x7f9a9f985780 (LWP 14877) "Main" 0x00007f9a9ee15a4a in waitpid () from /lib/x86_64-linux-gnu/libpthread.so.0 2 Thread 0x7f9a9dfff700 (LWP 14878) "SGen worker" 0x00007f9a9ee11072 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/x86_64-linux-gnu/libpthread.so.0 3 Thread 0x7f9a9bc34700 (LWP 14879) "Finalizer" 0x00007f9a9ee13f96 in do_futex_wait.constprop () from /lib/x86_64-linux-gnu/libpthread.so.0 4 Thread 0x7f9a8e3ba700 (LWP 14885) "Main" 0x00007f9a9e91006d in read () from /lib/x86_64-linux-gnu/libc.so.6 5 Thread 0x7f9a8e1b9700 (LWP 14886) "Main" 0x00007f9a9ee11786 in pthread_cond_timedwait@@GLIBC_2.3.2 () from /lib/x86_64-linux-gnu/libpthread.so.0 6 Thread 0x7f9a8e178700 (LWP 14887) "Threadpool work" 0x00007f9a9ee11786 in pthread_cond_timedwait@@GLIBC_2.3.2 () from /lib/x86_64-linux-gnu/libpthread.so.0 7 Thread 0x7f9a8df77700 (LWP 14888) "Threadpool work" 0x00007f9a9ee11786 in pthread_cond_timedwait@@GLIBC_2.3.2 () from /lib/x86_64-linux-gnu/libpthread.so.0 8 Thread 0x7f9a8d4fe700 (LWP 14890) "Threadpool work" 0x00007f9a9ee11786 in pthread_cond_timedwait@@GLIBC_2.3.2 () from /lib/x86_64-linux-gnu/libpthread.so.0 9 Thread 0x7f9a8d27b700 (LWP 14891) "Threadpool work" 0x00007f9a9ee11786 in pthread_cond_timedwait@@GLIBC_2.3.2 () from /lib/x86_64-linux-gnu/libpthread.so.0 10 Thread 0x7f9a8d07a700 (LWP 14892) "Threadpool work" 0x00007f9a9ee11786 in pthread_cond_timedwait@@GLIBC_2.3.2 () from /lib/x86_64-linux-gnu/libpthread.so.0 Thread 10 (Thread 0x7f9a8d07a700 (LWP 14892)): #0 0x00007f9a9ee11786 in pthread_cond_timedwait@@GLIBC_2.3.2 () at /lib/x86_64-linux-gnu/libpthread.so.0 #1 0x000055a1ef280ed6 in () #2 0x000055a1ef27abe1 in () #3 0x000055a1ef33a14a in () #4 0x00007f9a9ee0a7fc in start_thread () at /lib/x86_64-linux-gnu/libpthread.so.0 #5 0x00007f9a9e920b5f in clone () at /lib/x86_64-linux-gnu/libc.so.6 Thread 9 (Thread 0x7f9a8d27b700 (LWP 14891)): #0 0x00007f9a9ee11786 in pthread_cond_timedwait@@GLIBC_2.3.2 () at /lib/x86_64-linux-gnu/libpthread.so.0 #1 0x000055a1ef280ed6 in () #2 0x000055a1ef27abe1 in () #3 0x000055a1ef33a14a in () #4 0x00007f9a9ee0a7fc in start_thread () at /lib/x86_64-linux-gnu/libpthread.so.0 #5 0x00007f9a9e920b5f in clone () at /lib/x86_64-linux-gnu/libc.so.6 Thread 8 (Thread 0x7f9a8d4fe700 (LWP 14890)): #0 0x00007f9a9ee11786 in pthread_cond_timedwait@@GLIBC_2.3.2 () at /lib/x86_64-linux-gnu/libpthread.so.0 #1 0x000055a1ef280ed6 in () #2 0x000055a1ef27abe1 in () #3 0x000055a1ef33a14a in () #4 0x00007f9a9ee0a7fc in start_thread () at /lib/x86_64-linux-gnu/libpthread.so.0 #5 0x00007f9a9e920b5f in clone () at /lib/x86_64-linux-gnu/libc.so.6 Thread 7 (Thread 0x7f9a8df77700 (LWP 14888)): #0 0x00007f9a9ee11786 in pthread_cond_timedwait@@GLIBC_2.3.2 () at /lib/x86_64-linux-gnu/libpthread.so.0 #1 0x000055a1ef280ed6 in () #2 0x000055a1ef27abe1 in () #3 0x000055a1ef33a14a in () #4 0x00007f9a9ee0a7fc in start_thread () at /lib/x86_64-linux-gnu/libpthread.so.0 #5 0x00007f9a9e920b5f in clone () at /lib/x86_64-linux-gnu/libc.so.6 Thread 6 (Thread 0x7f9a8e178700 (LWP 14887)): #0 0x00007f9a9ee11786 in pthread_cond_timedwait@@GLIBC_2.3.2 () at /lib/x86_64-linux-gnu/libpthread.so.0 #1 0x000055a1ef280ed6 in () #2 0x000055a1ef27abe1 in () #3 0x000055a1ef33a14a in () #4 0x00007f9a9ee0a7fc in start_thread () at /lib/x86_64-linux-gnu/libpthread.so.0 #5 0x00007f9a9e920b5f in clone () at /lib/x86_64-linux-gnu/libc.so.6 Thread 5 (Thread 0x7f9a8e1b9700 (LWP 14886)): #0 0x00007f9a9ee11786 in pthread_cond_timedwait@@GLIBC_2.3.2 () at /lib/x86_64-linux-gnu/libpthread.so.0 #1 0x000055a1ef338e7f in () #2 0x000055a1ef27fe0e in () #3 0x000055a1ef27abe1 in () #4 0x000055a1ef33a14a in () #5 0x00007f9a9ee0a7fc in start_thread () at /lib/x86_64-linux-gnu/libpthread.so.0 #6 0x00007f9a9e920b5f in clone () at /lib/x86_64-linux-gnu/libc.so.6 Thread 4 (Thread 0x7f9a8e3ba700 (LWP 14885)): #0 0x00007f9a9e91006d in read () at /lib/x86_64-linux-gnu/libc.so.6 #1 0x0000000040932490 in () #2 0x00007f9a9e39eb98 in () #3 0x00007f9a9e39ed90 in () #4 0x00007f9a9e39f588 in () #5 0x0000000000000040 in () #6 0x00007f9a9e39ea38 in () #7 0x00007f9a88001bd0 in () #8 0x00007f9a8e3b9810 in () #9 0x00007f9a8e3b9810 in () #10 0x00007f9a8e3b9730 in () #11 0x0000000040932254 in () #12 0x000000000000000d in () #13 0x0000000000000000 in () Thread 3 (Thread 0x7f9a9bc34700 (LWP 14879)): #0 0x00007f9a9ee13f96 in do_futex_wait.constprop () at /lib/x86_64-linux-gnu/libpthread.so.0 #1 0x00007f9a9ee14054 in __new_sem_wait_slow.constprop.0 () at /lib/x86_64-linux-gnu/libpthread.so.0 #2 0x00007f9a9ee14144 in sem_wait@@GLIBC_2.2.5 () at /lib/x86_64-linux-gnu/libpthread.so.0 #3 0x000055a1ef29cdc9 in () #4 0x000055a1ef27abe1 in () #5 0x000055a1ef33a14a in () #6 0x00007f9a9ee0a7fc in start_thread () at /lib/x86_64-linux-gnu/libpthread.so.0 #7 0x00007f9a9e920b5f in clone () at /lib/x86_64-linux-gnu/libc.so.6 Thread 2 (Thread 0x7f9a9dfff700 (LWP 14878)): #0 0x00007f9a9ee11072 in pthread_cond_wait@@GLIBC_2.3.2 () at /lib/x86_64-linux-gnu/libpthread.so.0 #1 0x000055a1ef308863 in () #2 0x00007f9a9ee0a7fc in start_thread () at /lib/x86_64-linux-gnu/libpthread.so.0 #3 0x00007f9a9e920b5f in clone () at /lib/x86_64-linux-gnu/libc.so.6 Thread 1 (Thread 0x7f9a9f985780 (LWP 14877)): #0 0x00007f9a9ee15a4a in waitpid () at /lib/x86_64-linux-gnu/libpthread.so.0 #1 0x000055a1ef1805f0 in () #2 0x000055a1ef1d97ce in () #3 0x000055a1ef0f57e3 in () #4 0x00007f9a9ee16150 in () at /lib/x86_64-linux-gnu/libpthread.so.0 #5 0x00007f9a9e8b4476 in () at /lib/x86_64-linux-gnu/libc.so.6 #6 0x00007f9a9a9aa7ee in _XimLocalUtf8LookupString () at /usr/lib/x86_64-linux-gnu/libX11.so.6 #7 0x00000000409f0b45 in () #8 0x0000000000000000 in () ================================================================= Got a SIGSEGV while executing native code. This usually indicates a fatal error in the mono runtime or one of the native libraries used by your application. ================================================================= Aborted (core dumped) later errors: at <0xffffffff> at (wrapper managed-to-native) System.Windows.Forms.X11Keyboard.Xutf8LookupString (intptr,System.Windows.Forms.XEvent&,byte[],int,intptr&,System.Windows.Forms.XLookupStatus&) <0x000a4> at System.Windows.Forms.X11Keyboard.LookupString (System.Windows.Forms.XEvent&,int,System.Windows.Forms.XKeySym&,System.Windows.Forms.XLookupStatus&) <0x000c3> at System.Windows.Forms.X11Keyboard.EventToVkey (System.Windows.Forms.XEvent) <0x0003f> at System.Windows.Forms.X11Keyboard.ToUnicode (int,int,string&) <0x0035f> at System.Windows.Forms.X11Keyboard.TranslateMessage (System.Windows.Forms.MSG&) <0x00127> at System.Windows.Forms.XplatUIX11.TranslateMessage (System.Windows.Forms.MSG&) <0x00027> at System.Windows.Forms.XplatUI.TranslateMessage (System.Windows.Forms.MSG&) <0x00024> at System.Windows.Forms.Application.RunLoop (bool,System.Windows.Forms.ApplicationContext) <0x00da7> at System.Windows.Forms.Application.Run (System.Windows.Forms.ApplicationContext) <0x0005b> at System.Windows.Forms.Application.Run (System.Windows.Forms.Form) <0x00037> at KeePass.Program.Main (string[]) <0x00e0b> at (wrapper runtime-invoke) .runtime_invoke_void_object (object,intptr,intptr,intptr) <0x000d1> Native stacktrace: /usr/bin/cli(+0xc8514) [0x55c3ca9da514] /usr/bin/cli(+0x1217ce) [0x55c3caa337ce] /usr/bin/cli(+0x3d7e3) [0x55c3ca94f7e3] /lib/x86_64-linux-gnu/libpthread.so.0(+0x13150) [0x7f8166262150] /lib/x86_64-linux-gnu/libc.so.6(+0xa8476) [0x7f8165d00476] /usr/lib/x86_64-linux-gnu/libX11.so.6(_XimLocalUtf8LookupString+0xde) [0x7f8161daa7ee] [0x40eb30a5] Debug info from gdb: [New LWP 15010] [New LWP 15011] [New LWP 15017]