CVE-2025-21566

Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Optimizer). ...

6.5 Medium

Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Optimizer). Supported versions that are affected are 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).

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: Low
User interaction: None

What an attacker can affect

Confidentiality: None
Integrity: None
Availability: High

Exploit likelihood

0.72%Up 0.7 points since Jan 22, 2025

What each source reports

CVE List Score used 6.5

Record: CVE-2025-21566
CVSS 3.1: 6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Weakness: CWE-732
Updated: 2026-11-02

EUVDEUVD-2025-2555 6.5

Record: EUVD-2025-2555
CVSS 3.1: 6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

GitHub AdvisoriesGHSA-4x4h-rvfw-x95m 6.5

Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Optimizer). ...

Record: GHSA-4x4h-rvfw-x95m
CVSS 3.1: 6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Weakness: CWE-732
Updated: 2026-11-02

NVD 6.5

Record: CVE-2025-21566
CVSS 3.1: 6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Weakness: CWE-732
Updated: 2026-11-02

OSV 6.5

Record: CVE-2025-21566
CVSS 3.1: 6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

OSVUBUNTU-CVE-2025-21566 6.5

Record: UBUNTU-CVE-2025-21566
CVSS 3.1: 6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

Affected products

Affected packages

Affected packages
Package	Affected	Fixed
`percona-server-5.6` Ubuntu:16.04:LTS	All versions, plus listed versions 5.6.22-rel71.0-0ubuntu25.6.22-rel71.0-0ubuntu45.6.22-rel71.0-0ubuntu4.1	None known
`percona-xtradb-cluster-5.6` Ubuntu:16.04:LTS	All versions, plus listed versions 5.6.21-25.8-0ubuntu25.6.21-25.8-0ubuntu35.6.21-25.8-0ubuntu3.15.6.21-25.8-0ubuntu3.25.6.34-26.19-0ubuntu0.16.04.15.6.34-26.19-0ubuntu0.16.04.25.6.37-26.21-0ubuntu0.16.04.15.6.37-26.21-0ubuntu0.16.04.2	None known

History

History
Recorded	Changed	Sources
Nov 2, 2026	first indexed	CVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2025-21566 is a medium vulnerability (CVSS 6.5) in Oracle Mysql Server, published January 21, 2025. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.72%, the 54th percentile. No source names a fixed version.