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CVE Record

CVE-2021-2166: Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: DML).

Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: DML). Supported versions that are affected are 5.7.33 and prior and 8.0.23 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. 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-2021-2166 is a MySQL Server denial-of-service issue. A highly privileged user who can reach MySQL over the network may cause the server to hang or crash repeatedly. It does not indicate data theft or tampering, but it can disrupt database availability for dependent applications.

Executive priority

Treat as a moderate availability risk. Prioritize remediation for business-critical MySQL services and internet- or broadly network-reachable databases. Lower urgency is reasonable for isolated systems with tightly controlled privileged access, but unsupported or unpatched MySQL should still be addressed.

Technical view

The issue affects Oracle MySQL Server DML handling in supported versions 5.7.33 and prior and 8.0.23 and prior. CVSS 3.1 is 4.9: network attack vector, low complexity, high privileges required, no user interaction, availability high, confidentiality and integrity unaffected.

Likely exposure

Exposure is most likely where affected MySQL versions remain deployed, especially if privileged database accounts can connect over network-accessible MySQL protocols. Fedora, Gentoo, NetApp, and Oracle references indicate downstream and vendor-tracked impact, but the bundle does not identify every packaged product or appliance version.

Exploitation context

The source bundle does not show CISA KEV listing or confirmed active exploitation. Exploitation requires a high-privileged attacker with network access. The business impact is service interruption, not direct compromise of data confidentiality or integrity based on the provided CVSS vector.

Researcher notes

No CWE is provided in the bundle. The key constraints are PR:H and A:H: this is mainly a post-privilege availability bug in Server:DML. Avoid assuming unauthenticated exploitability or data exposure without additional vendor or incident evidence.

Mitigation direction

  • Apply Oracle April 2021 CPU guidance or supported vendor package updates.
  • Upgrade affected MySQL Server deployments beyond 5.7.33 and 8.0.23 per vendor guidance.
  • Restrict MySQL network access to trusted application and administration hosts.
  • Review and reduce high-privilege MySQL accounts with network login capability.
  • Check Fedora, Gentoo, NetApp, or other supplier advisories for packaged deployments.

Validation and detection

  • Inventory MySQL Server versions across production, staging, and embedded deployments.
  • Flag MySQL 5.7.33 or earlier and 8.0.23 or earlier as affected.
  • Confirm installed packages include the relevant Oracle or downstream security update.
  • Review MySQL grants for high-privilege users with remote access.
  • Check database logs and monitoring for unexplained hangs or repeated crashes.
Prepared
Confidence
high
Sources
12

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-2021-2166 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
11Source 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-2021-2166Attack 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 Server5.7.33 and prior, 8.0.23 and priorListed
Weakness

CWE details

No CWE listed

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