CVE-2026-34303
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 8.0.0-8.0.45, 8.4.0-8.4.8 and 9.0.0-9.6.0. 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 confidenceDenial of Service vulnerability in MySQL Server's Optimizer component. A low-privileged attacker with network access can cause MySQL Server to hang or crash repeatedly, resulting in complete availability loss. The CVSS vector shows high availability impact (A:H) with low attack complexity and only low privileges required.
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, <= 8.0.45>= 8.4.0, <= 8.4.8>= 9.0.0, <= 9.6.0CVSS 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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Retrieve MySQL Server versionRun `mysql --version` or connect to MySQL and execute `SELECT VERSION();`Affected if The version returned falls within 8.0.0-8.0.45, 8.4.0-8.4.8, or 9.0.0-9.6.0
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Verify MySQL is network-accessibleCheck if the MySQL port (default 3306) is exposed to network by reviewing firewall rules or running `netstat -tlnp | grep 3306` or `ss -tlnp | grep 3306`Affected if MySQL is listening on a network interface accessible to untrusted users
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Confirm low-privileged network users existReview MySQL user accounts with network access by running `SELECT user, host FROM mysql.user WHERE user NOT IN ('root','mysql.sys') AND host NOT IN ('localhost');`Affected if Any network-accessible MySQL user account exists (the vulnerability can be exploited with low-privileged access)
If the installed MySQL version is within 8.0.0-8.0.45, 8.4.0-8.4.8, or 9.0.0-9.6.0 AND the server is network-accessible with any low-privileged user account, the environment is affected by this CVE.
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 Critical Patch Update or upgrade to a patched version outside the affected ranges (8.0.0-8.0.45, 8.4.0-8.4.8, 9.0.0-9.6.0). Restrict network access to MySQL servers and follow least-privilege principles for database users.
Upgrade to MySQL 8.0.46 (if on 8.0.x), 8.4.9 (if on 8.4.x), or 9.7.0 (if on 9.x)
- 1. Identify your current MySQL Server version using: SELECT VERSION();
- 2. Determine which upgrade path applies: 8.0.x line → upgrade to 8.0.46; 8.4.x line → upgrade to 8.4.9; 9.x line → upgrade to 9.7.0
- 3. Review the MySQL release notes for the target version for any known issues
- 4. Create full backups of all databases using mysqldump or MySQL Enterprise Backup
- 5. Test the upgrade in a non-production environment first
- 6. Schedule a maintenance window with appropriate downtime
- 7. Stop the MySQL Server service
- 8. Upgrade MySQL Server packages to the fixed version using your OS package manager (e.g., yum update mysql-server, apt update mysql-server, or download from MySQL website)
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-2026-34303 — 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-2026-34303 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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