
Consider the test case below.

```sql
DROP TABLE t0;
DROP TABLE t1;

CREATE TABLE t0(c0 VARCHAR(500), PRIMARY KEY(c0));
CREATE TABLE t1(c0 INTEGER, PRIMARY KEY(c0));
INSERT INTO t1(c0) VALUES (1);


SELECT * FROM t1, t0 WHERE ((t0.c0)>((CASE t1.c0 WHEN 'a' THEN NULL END )));
-- *** Error 08S01: [Virtuoso Driver]CL065: Lost connection to server
```

This query would cause a crash.


I build docker image following this: https://github.com/openlink/vos-reference-docker. Kindly inform me if I did something wrong or I should provide more information (e.g. backtrace).

Here's the version: Version 7.2.13-dev.3239-pthreads as of Mar 13 2024 (bb53b41)
Crash by `CASE WHEN`
This is a GitHub Issue
repo:virtuoso-opensource
owner:openlink
Title : Crash by `CASE WHEN`
Issue date:

--- start body ---

Consider the test case below.

```sql
DROP TABLE t0;
DROP TABLE t1;

CREATE TABLE t0(c0 VARCHAR(500), PRIMARY KEY(c0));
CREATE TABLE t1(c0 INTEGER, PRIMARY KEY(c0));
INSERT INTO t1(c0) VALUES (1);


SELECT * FROM t1, t0 WHERE ((t0.c0)>((CASE t1.c0 WHEN 'a' THEN NULL END )));
-- *** Error 08S01: [Virtuoso Driver]CL065: Lost connection to server
```

This query would cause a crash.


I build docker image following this: https://github.com/openlink/vos-reference-docker. Kindly inform me if I did something wrong or I should provide more information (e.g. backtrace).

Here's the version: Version 7.2.13-dev.3239-pthreads as of Mar 13 2024 (bb53b41)
--- end body ---

A crash occurs in Virtuoso when executing a SQL query that includes a `CASE WHEN` statement with a comparison to a NULL value. This indicates a potential vulnerability that could be exploited to cause a Denial of Service (DoS) by crashing the server.