Upstream MySQL 5.6.20 is also affected:

openxs@ao756:~/dbs/5.6$ bash ~/ps_crash.sh
ERROR 2013 (HY000) at line 1: Lost connection to MySQL server during query
openxs@ao756:~/dbs/5.6$ 140906 15:49:16 mysqld_safe Number of processes running now: 0
140906 15:49:16 mysqld_safe mysqld restarted

openxs@ao756:~/dbs/5.6$ tail -100 data/ao756.err
2014-09-06 15:47:28 8383 [Note] InnoDB: Highest supported file format is Barracuda.
2014-09-06 15:47:28 8383 [Note] InnoDB: 128 rollback segment(s) are active.
2014-09-06 15:47:28 8383 [Note] InnoDB: Waiting for purge to start
2014-09-06 15:47:28 8383 [Note] InnoDB: 5.6.20 started; log sequence number 265035407
2014-09-06 15:47:28 8383 [Warning] Plugin validate_password reported: 'Dictionary file not specified'
2014-09-06 15:47:28 8383 [Note] Server hostname (bind-address): '*'; port: 3306
2014-09-06 15:47:28 8383 [Note] IPv6 is available.
2014-09-06 15:47:28 8383 [Note]   - '::' resolves to '::';
2014-09-06 15:47:28 8383 [Note] Server socket created on IP: '::'.
2014-09-06 15:47:29 8383 [Note] Event Scheduler: Loaded 0 events
2014-09-06 15:47:29 8383 [Note] /home/openxs/dbs/5.6/bin/mysqld: ready for connections.
Version: '5.6.20'  socket: '/tmp/mysql.sock'  port: 3306  MySQL Community Server (GPL)
12:49:16 UTC - mysqld got signal 11 ;
This could be because you hit a bug. It is also possible that this binary
or one of the libraries it was linked against is corrupt, improperly built,
or misconfigured. This error can also be caused by malfunctioning hardware.
We will try our best to scrape up some info that will hopefully help
diagnose the problem, but since we have already crashed,
something is definitely wrong and this may fail.

key_buffer_size=8388608
read_buffer_size=131072
max_used_connections=1
max_threads=151
thread_count=1
connection_count=1
It is possible that mysqld could use up to
key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 68245 K  bytes of memory
Hope that's ok; if not, decrease some variables in the equation.

Thread pointer: 0x2755730
Attempting backtrace. You can use the following information to find out
where mysqld died. If you see no messages after this, something went
terribly wrong...
stack_bottom = 7f07c0281e50 thread_stack 0x40000
/home/openxs/dbs/5.6/bin/mysqld(my_print_stacktrace+0x2c)[0x8cf1cc]
/home/openxs/dbs/5.6/bin/mysqld(handle_fatal_signal+0x481)[0x66cda1]
/lib/x86_64-linux-gnu/libpthread.so.0(+0x10340)[0x7f07d406a340]
/lib/x86_64-linux-gnu/libc.so.6(+0x1419b4)[0x7f07d35b59b4]
/home/openxs/dbs/5.6/bin/mysqld(_ZNSt8_Rb_treeIP14dict_foreign_tS1_St9_IdentityIS1_E20dict_foreign_compareSaIS1_EE11equal_rangeERKS1_+0x9d)[0xa777ed]
/home/openxs/dbs/5.6/bin/mysqld[0xa7721a]
/home/openxs/dbs/5.6/bin/mysqld[0x946851]
/home/openxs/dbs/5.6/bin/mysqld(_Z17mysql_alter_tableP3THDPcS1_P24st_ha_create_informationP10TABLE_LISTP10Alter_infojP8st_orderb+0x2a89)[0x737509]
/home/openxs/dbs/5.6/bin/mysqld(_ZN19Sql_cmd_alter_table7executeEP3THD+0x49d)[0x81122d]
/home/openxs/dbs/5.6/bin/mysqld(_Z21mysql_execute_commandP3THD+0x33de)[0x6e88ce]
/home/openxs/dbs/5.6/bin/mysqld(_Z11mysql_parseP3THDPcjP12Parser_state+0x378)[0x6ebb58]
/home/openxs/dbs/5.6/bin/mysqld(_Z16dispatch_command19enum_server_commandP3THDPcj+0xf89)[0x6ed269]
/home/openxs/dbs/5.6/bin/mysqld(_Z24do_handle_one_connectionP3THD+0x142)[0x6bbd92]
/home/openxs/dbs/5.6/bin/mysqld(handle_one_connection+0x40)[0x6bbe40]
/home/openxs/dbs/5.6/bin/mysqld(pfs_spawn_thread+0x143)[0xb15ce3]
/lib/x86_64-linux-gnu/libpthread.so.0(+0x8182)[0x7f07d4062182]
/lib/x86_64-linux-gnu/libc.so.6(clone+0x6d)[0x7f07d356efbd]

Trying to get some variables.
Some pointers may be invalid and cause the dump to abort.
Query (7f07a0005130): ALTER TABLE testTable17 DROP FOREIGN KEY testTable17_ibfk_1
Connection ID (thread ID): 3
Status: NOT_KILLED

Richard,

May I use your test script that demonstrates the bug in the upstream bug report or would you prefer to file upstream bug yourself?