CVE-2025-21500
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 8.0.40 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 confidenceCVE-2025-21500 is a denial-of-service vulnerability in the MySQL Server Optimizer component affecting versions 8.0.40 and prior, 8.4.3 and prior, and 9.1.0 and prior. An attacker with low-privileged network access can exploit this via multiple protocols to cause MySQL Server to hang or crash repeatedly.
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, <= 8.0.40>= 8.4.0, <= 8.4.3>= 9.0.0, <= 9.1.0CVSS 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.
-
Identify installed MySQL Server versionRun `mysql --version` from the MySQL client host, or execute `SELECT VERSION();` query against the MySQL serverAffected if The version falls within 8.0.0-8.0.40, 8.4.0-8.4.3, or 9.0.0-9.1.0
-
Verify MySQL network listening configurationCheck the MySQL configuration file (my.cnf or my.ini) for the `bind-address` setting, or query `SHOW VARIABLES LIKE 'bind_address';`Affected if The server is bound to 0.0.0.0 or an external IP address (not 127.0.0.1 or localhost-only)
-
Confirm network accessibility from untrusted sourcesAttempt to connect to MySQL port 3306 from a non-trusted network segment, or review firewall rules and network ACLs controlling access to the MySQL portAffected if MySQL port 3306 (or configured port) is reachable from low-privilege or untrusted network segments
You are affected if your MySQL version is 8.0.40 or lower, 8.4.3 or lower, or 9.1.0 or lower 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 Critical Patch Update (CPU) for January 2025 to obtain the patched MySQL version, or upgrade to a supported patched version of MySQL 8.0.x, 8.4.x, or 9.x.
MySQL 8.0.41+ (for 8.0.x), MySQL 8.4.4+ (for 8.4.x), or MySQL 9.2.0+ (for 9.x)
- 1. Identify the exact MySQL Server version currently installed using: SELECT VERSION();
- 2. For MySQL 8.0.x users: Upgrade to MySQL 8.0.41 or later
- 3. For MySQL 8.4.x users: Upgrade to MySQL 8.4.4 or later
- 4. For MySQL 9.x users: Upgrade to MySQL 9.2.0 or later
- 5. Download the appropriate MySQL Server installer from the official Oracle MySQL website (https://www.mysql.com/downloads/)
- 6. Before upgrading in production, test the upgrade in a staging environment
- 7. Perform a full backup of all databases before upgrading
- 8. Stop the MySQL Server service
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,600.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2025-21500 — 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-2025-21500 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
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
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.
- 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
- No spam, self-promotion, credentials, or personal data