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CVE Record

CVE-2026-21964: Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Thread Pooling).

Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Thread Pooling). Supported versions that are affected are 8.0.0-8.0.44, 8.4.0-8.4.7 and 9.0.0-9.5.0. 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. CVSS 3.1 Base Score 4.9 (Availability impacts). CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H).

MediumCVSS 4.9Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2026-21964 is a denial-of-service vulnerability in Oracle MySQL Server’s Thread Pooling component. A highly privileged attacker with network access can cause MySQL Server to hang or crash repeatedly. It does not indicate data theft or tampering, but it can disrupt database availability for affected MySQL versions.

Executive priority

Treat as a timely availability risk for business-critical MySQL systems. It is not described as a data breach issue, but a successful attack can stop database service. Prioritize patch planning and access review for critical or broadly reachable databases.

Technical view

Oracle reports affected MySQL Server versions 8.0.0-8.0.44, 8.4.0-8.4.7, and 9.0.0-9.5.0. CVSS 3.1 is 4.9: AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H. Impact is limited to availability, requiring high privileges and network access via multiple protocols.

Likely exposure

Exposure is most relevant where affected MySQL Server versions are reachable over a network by privileged database users or service accounts. Internet exposure is less central than credentialed access, but externally reachable MySQL increases operational risk.

Exploitation context

The provided sources do not report active exploitation, and the CVE is not listed as KEV. Exploitation requires high privileges, but Oracle describes it as easily exploitable once those privileges and network access exist.

Researcher notes

Public details are limited to Oracle’s advisory and CVE metadata. The vulnerability is in Server: Thread Pooling and causes complete denial of service. No CWE, proof of concept, exploit details, or named workaround were provided in the source bundle.

Mitigation direction

  • Identify MySQL Server instances running affected version ranges.
  • Review Oracle’s January 2026 Critical Patch Update for official remediation guidance.
  • Prioritize systems supporting critical applications or exposed to broad network access.
  • Restrict MySQL network access to trusted hosts and required service accounts.
  • Review privileged MySQL accounts and remove unnecessary access.

Validation and detection

  • Inventory MySQL Server versions across production and non-production environments.
  • Confirm whether Thread Pooling is relevant to deployed MySQL configurations.
  • Check which privileged accounts can connect over the network.
  • Verify remediation status against Oracle advisory guidance.
  • Monitor database availability logs for unexplained hangs or repeated crashes.
Prepared
Confidence
high
Sources
3

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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CVE-2026-21964 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
Medium
CVSS
4.9 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
0Timeline events
0ADP providers
2Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
4.9CVSS 3.1MediumCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H1.23.6Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

4.9Medium
CVSS 3.1 vector shape for CVE-2026-21964Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
Oracle CorporationMySQL Server8.0.0, 8.4.0, 9.0.0Listed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.