CVE-2024-21239 - DoS Vulnerability in Oracle MySQL’s InnoDB Component (Explained with Code, Exploit Details & References)

MySQL, one of the world’s most popular open-source relational database management systems, is frequently targeted by security researchers and attackers. In June 2024, Oracle acknowledged a serious Denial of Service (DoS) vulnerability in the MySQL Server product, specifically affecting the InnoDB storage engine. Assigned as CVE-2024-21239, this flaw enables an attacker with high privileges to crash the MySQL server or cause it to hang — impacting availability and bringing down services that rely on the database.

In this article, we’ll break down the vulnerability, show you a code example of how it can be triggered, and link to official resources for further reading.

What is CVE-2024-21239?

CVE-2024-21239 is a vulnerability found in Oracle MySQL Server’s InnoDB component. MySQL versions affected include:

Attack Complexity: Low (simple to execute)

- Privileges Required: High (attacker must be an authenticated high-privileged user, like DBA or root)

User Interaction: None (no tricking users)

- Impact: Availability — attacker can cause the MySQL Server to crash or hang repeatedly (full DoS)
- Confidentiality/Integrity: Not impacted (no data theft or modification)
- Base Score: 4.9 (Medium severity, CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H)

Oracle confirmed the details in its Critical Patch Update Advisory – July 2024.

How Does the Exploit Work?

This vulnerability is inside the InnoDB storage engine, which is used by default in modern MySQL installations. A high-privileged attacker can take advantage of a flaw in how InnoDB handles certain SQL queries or operations, causing MySQL to crash or enter a hung state.

Why Is This Dangerous?

- The attacker needs to be authenticated as a high-privileged user (like root or someone given ALL PRIVILEGES).

Proof of Concept (PoC) Example

> Disclaimer: The following is a simplified pseudocode example, not a crash weapon — it mirrors possible exploitation patterns based on public vulnerability characteristics.

-- You need SUPER or root privileges to execute these manipulating system-level queries.

-- Imagine a problematic use of RENAME, TRUNCATE, or certain ALTER TABLE queries
-- within complex transactions, which tickles the vulnerable InnoDB code path.

START TRANSACTION;
ALTER TABLE sensitive_table DISCARD TABLESPACE;  -- Drops the InnoDB tablespace
-- Later, try to access the same table in another transaction or session:
SELECT * FROM sensitive_table;  -- This can trigger MySQL to crash or hang

-- In a real-world crash sequence, the attacker might run this in rapid succession
-- or in multi-session scenarios, causing resource exhaustion and full DoS.

ROLLBACK; -- (Sometimes, rolling back or committing at this point worsens the impact)

Note: Specific inputs that trigger CVE-2024-21239 are not public to prevent widespread misuse. The pattern involves destructive InnoDB operations by high-privileged users combined in combinations that the internal InnoDB code fails to safely handle, leading to a crash.

Attacker connects remotely (e.g., via TCP or over SSH tunnel)

3. Using SQL queries that involve manipulating InnoDB tablespaces, truncating, or altering tables — possibly abusing system tables or metadata, the attacker causes a crash.
4. Each exploit attempt leads to a hard crash or deadlock of MySQL — requiring administrators to restart the service.
5. If an attacker makes the exploit repeatable (scripted), they can keep your MySQL down until the vulnerability is fixed.

Restrict High Privileges: Make sure only trusted admins have ‘root’ or ALL PRIVILEGES.

2. Update Immediately: If you run MySQL 8..39, 8.4.2, 9..1 (or earlier), apply the latest patches from Oracle:
- MySQL Community Edition Downloads
- Oracle Critical Patch Updates
3. Review Server Logs: Look for suspicious ALTER, RENAME, TRUNCATE, or transactions on InnoDB tables.
4. Monitor for Crashes: Frequent or unexplained server restarts could signal attempted exploitation.

References and Further Reading

- Oracle Critical Patch Update Advisory – July 2024
- NVD Entry for CVE-2024-21239 *(check for updates)*
- MySQL Release Notes *(see security fixes for your version)*

Conclusion

Though the attacker needs high privileges, CVE-2024-21239 is a straightforward way to disrupt services using vulnerable MySQL versions. This kind of DoS risk is serious for businesses that depend on MySQL for uptime and reliability.

The fix? Update your MySQL servers immediately, lock down privileged accounts, and monitor for suspicious administrative actions. Do not wait for a hang or crash to reveal your exposure!

Timeline

Published on: 10/15/2024 20:15:13 UTC
Last modified on: 10/16/2024 20:36:59 UTC