The PoC is generated by my DBMS fuzzer. It can also be reproduced in the beta docker image.
```SQL
CREATE TABLE v0 ( v1 INT NOT NULL NOT NULL NOT NULL CHECK ( v1 ) , v2 INT UNIQUE NOT NULL , v3 INT UNIQUE ) ;

 CREATE VIEW v4 AS SELECT * FROM v0 ORDER BY v1 + v3 , ( v2 + v2 ) / 2147483647 ;

 CREATE VIEW v7 AS SELECT v2 FROM ( SELECT v2 FROM v0 WHERE 8 IN ( 78222408.000000 ) GROUP BY v1 HAVING ( v3 >= 'x' AND v1 BETWEEN 6 AND 77 AND v2 = 23 ) ) AS v6 , v0 AS v5 NATURAL JOIN v4 WHERE v3 = 127 ;

 UPDATE v4 SET v3 = 0 WHERE v1 = ( SELECT -2147483648 FROM v0 AS v8 JOIN v7 ON v3 < ( SELECT v2 FROM v0 , v7 ) JOIN v0 USING ( v3 ) WHERE v2 = v3 ) ;
```

backtrace:
```c
#0 0x771632 (sqlo_natural_join_cond+0x1a2)
#1 0x772f4f (sqlo_add_table_ref+0xc0f)
#2 0x772cda (sqlo_add_table_ref+0x99a)
#3 0x77ee78 (sqlo_select_scope+0x6a8)
#4 0x76fe17 (sqlo_scope+0x447)
#5 0x7825ce (sqlo_scalar_subq_scope+0xfe)
#6 0x76fc2b (sqlo_scope+0x25b)
#7 0x76ff6b (sqlo_scope+0x59b)
#8 0x76ff5b (sqlo_scope+0x58b)
#9 0x77ef37 (sqlo_select_scope+0x767)
#10 0x76fe17 (sqlo_scope+0x447)
#11 0x70e851 (sqlo_top_2+0x41)
#12 0x70e465 (sqlo_top_1+0xf5)
#13 0x7101b1 (sqlo_query_spec+0x1a1)
#14 0x7e0258 (sqlc_update_searched+0x548)
#15 0x81aca1 (sqlc_update_view+0xaa1)
#16 0x7e08e0 (sqlc_update_searched+0xbd0)
#17 0x6b9ac2 (sql_stmt_comp+0x812)
#18 0x6bc9d2 (sql_compile_1+0x1a62)
#19 0x7cba60 (stmt_set_query+0x340)
#20 0x7cd952 (sf_sql_execute+0x922)
#21 0x7cecde (sf_sql_execute_w+0x17e)
#22 0x7d799d (sf_sql_execute_wrapper+0x3d)
#23 0xe214bc (future_wrapper+0x3fc)
#24 0xe28dbe (_thread_boot+0x11e)
#25 0x7fe87284d609 (start_thread+0xd9)
#26 0x7fe87261d133 (clone+0x43)
```

ways to reproduce (write poc to the file /tmp/test.sql first):
```bash
# remove the old one
docker container rm virtdb_test -f
# start virtuoso through docker
docker run --name virtdb_test -itd --env DBA_PASSWORD=dba  pkleef/virtuoso-opensource-7
# wait the server starting
sleep 10
# check whether the simple query works
echo "SELECT 1;" | docker exec -i virtdb_test isql 1111 dba
# run the poc
cat /tmp/test.sql | docker exec -i virtdb_test isql 1111 dba
```
Fuzzer: Virtuoso 7.2.11 crashed at `sqlo_natural_join_cond`
This is a GitHub Issue
repo:virtuoso-opensource
owner:openlink
Title : Fuzzer: Virtuoso 7.2.11 crashed at `sqlo_natural_join_cond`
Issue date:

--- start body ---
The PoC is generated by my DBMS fuzzer. It can also be reproduced in the beta docker image.
```SQL
CREATE TABLE v0 ( v1 INT NOT NULL NOT NULL NOT NULL CHECK ( v1 ) , v2 INT UNIQUE NOT NULL , v3 INT UNIQUE ) ;

 CREATE VIEW v4 AS SELECT * FROM v0 ORDER BY v1 + v3 , ( v2 + v2 ) / 2147483647 ;

 CREATE VIEW v7 AS SELECT v2 FROM ( SELECT v2 FROM v0 WHERE 8 IN ( 78222408.000000 ) GROUP BY v1 HAVING ( v3 >= 'x' AND v1 BETWEEN 6 AND 77 AND v2 = 23 ) ) AS v6 , v0 AS v5 NATURAL JOIN v4 WHERE v3 = 127 ;

 UPDATE v4 SET v3 = 0 WHERE v1 = ( SELECT -2147483648 FROM v0 AS v8 JOIN v7 ON v3 < ( SELECT v2 FROM v0 , v7 ) JOIN v0 USING ( v3 ) WHERE v2 = v3 ) ;
```

backtrace:
```c
#0 0x771632 (sqlo_natural_join_cond+0x1a2)
#1 0x772f4f (sqlo_add_table_ref+0xc0f)
#2 0x772cda (sqlo_add_table_ref+0x99a)
#3 0x77ee78 (sqlo_select_scope+0x6a8)
#4 0x76fe17 (sqlo_scope+0x447)
#5 0x7825ce (sqlo_scalar_subq_scope+0xfe)
#6 0x76fc2b (sqlo_scope+0x25b)
#7 0x76ff6b (sqlo_scope+0x59b)
#8 0x76ff5b (sqlo_scope+0x58b)
#9 0x77ef37 (sqlo_select_scope+0x767)
#10 0x76fe17 (sqlo_scope+0x447)
#11 0x70e851 (sqlo_top_2+0x41)
#12 0x70e465 (sqlo_top_1+0xf5)
#13 0x7101b1 (sqlo_query_spec+0x1a1)
#14 0x7e0258 (sqlc_update_searched+0x548)
#15 0x81aca1 (sqlc_update_view+0xaa1)
#16 0x7e08e0 (sqlc_update_searched+0xbd0)
#17 0x6b9ac2 (sql_stmt_comp+0x812)
#18 0x6bc9d2 (sql_compile_1+0x1a62)
#19 0x7cba60 (stmt_set_query+0x340)
#20 0x7cd952 (sf_sql_execute+0x922)
#21 0x7cecde (sf_sql_execute_w+0x17e)
#22 0x7d799d (sf_sql_execute_wrapper+0x3d)
#23 0xe214bc (future_wrapper+0x3fc)
#24 0xe28dbe (_thread_boot+0x11e)
#25 0x7fe87284d609 (start_thread+0xd9)
#26 0x7fe87261d133 (clone+0x43)
```

ways to reproduce (write poc to the file /tmp/test.sql first):
```bash
# remove the old one
docker container rm virtdb_test -f
# start virtuoso through docker
docker run --name virtdb_test -itd --env DBA_PASSWORD=dba  pkleef/virtuoso-opensource-7
# wait the server starting
sleep 10
# check whether the simple query works
echo "SELECT 1;" | docker exec -i virtdb_test isql 1111 dba
# run the poc
cat /tmp/test.sql | docker exec -i virtdb_test isql 1111 dba
```
--- end body ---
