CVE-2025-21501
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 confidenceDenial of service vulnerability in the MySQL Server Optimizer component. Low-privileged attackers with network access can exploit this flaw to cause the MySQL server to hang or crash repeatedly, 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, <= 8.0.40>= 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.
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Determine installed MySQL versionRun `mysql --version` or log into MySQL and execute `SELECT VERSION();`Affected if The version number falls within 8.0.0-8.0.40, 8.4.0-8.4.3, or 9.0.0-9.1.0
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Verify MySQL is listening on network interfacesCheck the MySQL configuration file (my.cnf or my.ini) for `bind-address` setting, or run `netstat -tlnp | grep 3306` to see if port 3306 is listening on a non-localhost addressAffected if MySQL is bound to 0.0.0.0 or a public IP address rather than 127.0.0.1 or localhost only
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Confirm network accessibility of MySQL portFrom an external host, attempt to reach the MySQL port with `nc -zv <host> 3306` or `telnet <host> 3306`Affected if The MySQL port is reachable from untrusted networks
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Review MySQL user accounts and privilegesLog into MySQL as an administrator and run `SELECT user, host, plugin FROM mysql.user;` to list all accountsAffected if There are any user accounts with privileges granted from non-localhost hosts (`%` or specific remote hosts)
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 MySQL security updates to upgrade to patched versions (8.0.41+, 8.4.4+, or 9.2.0+). If immediate patching is not possible, restrict network access to MySQL servers and limit privileged database accounts.
MySQL 8.0.41+ / 8.4.4+ / 9.1.1+ (upgrade to the latest available stable release in your respective branch)
- 1. Identify the current MySQL Server version 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 9.1.1 or later
- 5. Download the appropriate MySQL Server installer from the official Oracle MySQL downloads page (https://dev.mysql.com/downloads/mysql/)
- 6. Before upgrading, backup all databases using: mysqldump --all-databases --single-transaction --routines --triggers > backup.sql
- 7. Stop the MySQL Server service
- 8. Install the new MySQL Server version
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation3.0 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-2025-21501 — 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-2025-21501 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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- 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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