CVE-2026-21968
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedVulnerability in the MySQL Server product of Oracle MySQL (component: Server: Optimizer). Supported versions that are affected are 8.0.0-8.0.44, 8.4.0-8.4.7 and 9.0.0-9.5.0. Easily exploitable vulnerability allows low privileged attacker with network access via multiple protocols to compromise MySQL Server. Successful attacks of this vulnerability can result in unauthorized ability to cause a hang or frequently repeatable crash (complete DOS) of MySQL Server. CVSS 3.1 Base Score 6.5 (Availability impacts). CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H).
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceA denial-of-service vulnerability in the MySQL Server Optimizer component allows a low-privileged attacker with network access via multiple protocols to cause the MySQL server to hang or experience repeatable crashes, resulting in complete availability loss.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data>= 8.0.0, <= 8.0.44>= 8.4.0, <= 8.4.7>= 9.0.0, <= 9.5.0CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check installed MySQL versionRun `SELECT VERSION();` or `mysql --version` from the MySQL client or command lineAffected if The version falls within 8.0.0-8.0.44, 8.4.0-8.4.7, or 9.0.0-9.5.0
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Confirm network listener statusCheck MySQL configuration for `bind-address` setting in my.cnf/my.ini or run `SHOW VARIABLES LIKE 'bind_address';`Affected if MySQL is bound to 0.0.0.0 or a reachable network interface rather than 127.0.0.1 (localhost only)
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Verify protocol accessibilityTest TCP connectivity to MySQL port (default 3306) from a remote host using `nc -zv <host> 3306` or telnetAffected if Network access to the MySQL port is allowed from untrusted networks
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Identify low-privilege accounts with network accessRun `SELECT user, host, plugin FROM mysql.user WHERE Select_priv='Y' AND (user NOT IN ('root','mysql.sys','mysql.session','mysql.infoschema'));`Affected if Any non-admin users exist that can be used over the network to trigger the vulnerable Optimizer code path
You are affected if your MySQL version is within the affected ranges AND the server is accessible over the network to low-privileged users.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scopedApply Oracle's security patch by upgrading MySQL to a fixed version outside the affected ranges (8.0.0-8.0.44, 8.4.0-8.4.7, 9.0.0-9.5.0). As an interim control, restrict network exposure and enforce least-privilege user permissions on database accounts.
MySQL 8.0.45+ (or 8.4.8+ or 9.0.1+ depending on your current major version branch)
- 1. Backup your MySQL database using mysqldump or your preferred backup method
- 2. Stop the MySQL Server service
- 3. Update your package manager and upgrade MySQL Server to version 8.0.45 or higher for the 8.0.x branch, 8.4.8 or higher for the 8.4.x branch, or 9.0.1 or higher for the 9.x branch
- 4. Verify the installed version matches the target using: mysql --version
- 5. Start the MySQL Server service
- 6. Run mysql_upgrade to check and repair tables if needed
- 7. Verify the server is operational and test application connectivity
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation4.0 h
- Testing6.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-21968 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-21968 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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