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Mysql ClusterDatabase / datastore · Oracle

CVE-2025-21518

MEDIUM · 6.5 CVSS v3.1 Published 2025-01-21
Fix available
A fix is available. Upgrade to after 9.1.0 or later.
See remediation →
71/100
Remediation priority · Elevated
Remotely reachable Zero-click

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 · unedited
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Optimizer). Supported versions that are affected are 8.0.40 and prior, 8.4.3 and prior and 9.1.0 and prior. 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 confidence

A vulnerability in the MySQL Server Optimizer component allows low-privileged attackers with network access via multiple protocols to cause a denial of service by hanging or crashing the MySQL Server. The issue affects versions 8.0.40 and prior, 8.4.3 and prior, and 9.1.0 and prior.

MitigationApply Oracle MySQL security updates for versions 8.0.41, 8.4.4, and 9.1.1 or later to patch the Optimizer vulnerability. Prior to production deployment, test in a staging environment to ensure compatibility with existing applications.

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
Mysql ClusterDatabase / datastore
Affected:>= 7.6.0, <= 7.6.32>= 8.0.0, <= 8.0.40>= 8.4.0, <= 8.4.3>= 9.0.0, <= 9.1.0
Mysql ServerDatabase / datastore
Affected:>= 8.0.0, <= 8.0.40>= 8.4.0, <= 8.4.3>= 9.0.0, <= 9.1.0

CVSS 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 checks

Work through these to decide whether this CVE applies to you.

  1. Check MySQL Server version
    Run `mysql --version` from command line or execute `SELECT VERSION();` as a database user
    Affected if Version is 8.0.40 or lower, or 8.4.3 or lower, or 9.1.0 or lower (within 8.0.0-8.0.40, 8.4.0-8.4.3, or 9.0.0-9.1.0 ranges)
  2. Check MySQL Cluster version
    Run `mysqld --version` or check the MySQL Cluster service version if using MySQL Cluster instead of MySQL Server
    Affected if Version is 7.6.32 or lower, or within 8.0.0-8.0.40, 8.4.0-8.4.3, or 9.0.0-9.1.0 ranges
  3. Verify MySQL network listening status
    Check if mysqld is bound to network interfaces: run `netstat -tlnp | grep 3306` or `ss -tlnp | grep 3306` to see if port 3306 (default MySQL port) is listening on non-loopback addresses
    Affected if MySQL is listening on network-accessible interfaces (0.0.0.0 or specific IP rather than only 127.0.0.1)
  4. Confirm low-privileged user access possibility
    Review if network users with low privileges can connect: check user grant tables with `SELECT user, host FROM mysql.user;` and verify authentication settings
    Affected if Network access is enabled and low-privileged users can authenticate from remote hosts

Environment is affected if running MySQL Server or MySQL Cluster versions within the listed ranges AND the MySQL service is accessible over the network, allowing low-privileged remote attackers to trigger the Optimizer DoS condition.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 · scoped
Upgrade available Upgrade to a release after 9.1.0
Interim mitigation

Apply Oracle MySQL security updates for versions 8.0.41, 8.4.4, and 9.1.1 or later to patch the Optimizer vulnerability. Prior to production deployment, test in a staging environment to ensure compatibility with existing applications.

Recommended fix High confidence

MySQL Server 8.0.41+, 8.4.4+, or 9.2.0+ | MySQL Cluster 7.6.33+, 8.0.41+, 8.4.4+, or 9.2.0+

  1. 1. Identify the currently installed MySQL Server or MySQL Cluster version using: `mysql --version` or `SELECT VERSION();`
  2. 2. For MySQL Server: upgrade to version 8.0.41 or later, 8.4.4 or later, or 9.2.0 or later
  3. 3. For MySQL Cluster: upgrade to version 7.6.33 or later, 8.0.41 or later, 8.4.4 or later, or 9.2.0 or later
  4. 4. Back up all databases before performing the upgrade
  5. 5. Review the MySQL upgrade guide for your version: https://dev.mysql.com/doc/refman/8.0/en/upgrading.html
  6. 6. Perform the upgrade using your system's package manager or by downloading from https://dev.mysql.com/downloads/mysql/
  7. 7. After upgrade, verify the MySQL service is running and test critical queries
  8. 8. Ensure the new version is confirmed by running: `SELECT VERSION();`
Caveat Review MySQL release notes for each version jump for potential migration requirements, especially when moving from 8.0.x to 8.4.x or 9.x as some features may be deprecated

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Mysql Cluster Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing3.0 h
  • Review / QA2.0 h
9.0 hours of engineering $1,570
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-21518 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
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