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CVE-2025-21501: 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

mediumCVSS 6.5CVE-2025-21501

CSIRTS triage

vendor: Oracleproduct: MySQL ServerInformation disclosureaffected: 8.0.40 and prior, 8.4.3 and prior, 9.1.0 and prior
What
Optimizer component vulnerability allowing low-privileged attacker to access unauthorized information via network.
Who is affected
MySQL Server deployments with versions 8.0.40, 8.4.3, or 9.1.0 and prior accessible from network.
Urgency
Medium severity (CVSS 6.5); requires network access and low privileges but information disclosure impact warrants timely patching.
Action
Upgrade MySQL Server to a version after 8.0.40, 8.4.3, or 9.1.0 respectively.

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Details

Source
Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity
medium — CVSS 6.5
Published
2026-08-06
Exploitation
Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-21501

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-2025-21501coverage & exploitation statusNVD · CVE.org

Recent advisories for MySQL Server product

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

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