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CVE-2025-21555: Vulnerability in the MySQL Server product of Oracle MySQL (component: InnoDB). 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 high 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 as well as unau

mediumCVSS 5.5CVE-2025-21555

CSIRTS triage

vendor: Oracleproduct: MySQL ServerOtheraffected: 8.0.40 and prior, 8.4.3 and prior, 9.1.0 and prior
What
An easily exploitable vulnerability in the InnoDB component allows a high-privileged attacker with network access to cause unspecified impact via multiple protocols.
Who is affected
MySQL Server deployments on versions 8.0.40, 8.4.3, and 9.1.0 or earlier.
Urgency
Medium severity (CVSS 5.5) and not currently exploited; remediation needed for affected versions.
Action
Update MySQL Server to versions 8.0.41, 8.4.4, 9.1.1 or later as appropriate for your deployment.

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Details

Source
Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity
medium — CVSS 5.5
Published
2026-08-06
Exploitation
Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-21555

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Referenced CVEs

CVECSIRTS overviewExternal
CVE-2025-21555coverage & exploitation statusNVD · CVE.org

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