Submitted by: @pavel-zotov

Attachments:
firebird.4068.WI-T4_0_0_1036.stack_trace.7z
firebird.4488.WI-T4_0_0_1036.stack_trace.7z

Adjust path and name of database in following script.
Then run it:

shell del C:\\FBTESTING\\qa\\fbt\-repo\\tmp\\c5593\.fdb 2\>nul;

set wng off;
set list on;
set echo on;
set bail on;

set names utf8;
create database 'localhost:C:\\FBTESTING\\qa\\fbt\-repo\\tmp\\c5593\.fdb';

revoke all on all from any\_name\_here;
commit;
quit;

===

Output will be (as reply on 'revoke all on all from any_name_here;'):

Statement failed, SQLSTATE = 08006
Error reading data from the connection.
After line 9 in file c5593a.sql
Statement failed, SQLSTATE = 08006
Error writing data to the connection.
-send_packet/send

It seems that only 4.x if affected, no such error on 3.0.4.32997.

Link to folder where FB distr + dumps + stack traces can be found:

https://drive.google.com/drive/folders/1sqgNBuR78J97Q3kAy4-2SCp5alxnuTa_